diff --git a/.gitignore b/.gitignore
index 78b77fb..7701e77 100644
--- a/.gitignore
+++ b/.gitignore
@@ -71,4 +71,6 @@ target/
 .DS_Store
 *.pem
 .history
-tsconfig.tsbuildinfo
\ No newline at end of file
+tsconfig.tsbuildinfo
+
+test.py
\ No newline at end of file
diff --git a/plane/__init__.py b/plane/__init__.py
index 69e8bf5..943947f 100644
--- a/plane/__init__.py
+++ b/plane/__init__.py
@@ -2,6 +2,7 @@
 from .api.cycles import Cycles
 from .api.initiatives import Initiatives
 from .api.labels import Labels
+from .api.milestones import Milestones
 from .api.modules import Modules
 from .api.pages import Pages
 from .api.projects import Projects
@@ -40,6 +41,7 @@
     "Initiatives",
     "Teamspaces",
     "Users",
+    "Milestones",
     "Modules",
     "Cycles",
     "Pages",
diff --git a/plane/api/milestones.py b/plane/api/milestones.py
new file mode 100644
index 0000000..1ae110b
--- /dev/null
+++ b/plane/api/milestones.py
@@ -0,0 +1,145 @@
+from __future__ import annotations
+
+from collections.abc import Mapping
+from typing import Any
+
+from ..models.milestones import (
+    CreateMilestone,
+    Milestone,
+    MilestoneWorkItem,
+    PaginatedMilestoneResponse,
+    PaginatedMilestoneWorkItemResponse,
+    UpdateMilestone,
+)
+from .base_resource import BaseResource
+
+
+class Milestones(BaseResource):
+    def __init__(self, config: Any) -> None:
+        super().__init__(config, "/workspaces/")
+
+    def create(self, workspace_slug: str, project_id: str, data: CreateMilestone) -> Milestone:
+        """Create a new milestone.
+
+        Args:
+            workspace_slug: The workspace slug identifier
+            project_id: UUID of the project
+            data: Milestone data
+        """
+        response = self._post(
+            f"{workspace_slug}/projects/{project_id}/milestones",
+            data.model_dump(exclude_none=True),
+        )
+        return Milestone.model_validate(response)
+
+    def retrieve(self, workspace_slug: str, project_id: str, milestone_id: str) -> Milestone:
+        """Retrieve a milestone by ID.
+
+        Args:
+            workspace_slug: The workspace slug identifier
+            project_id: UUID of the project
+            milestone_id: UUID of the milestone
+        """
+        response = self._get(f"{workspace_slug}/projects/{project_id}/milestones/{milestone_id}")
+        return Milestone.model_validate(response)
+
+    def update(
+        self, workspace_slug: str, project_id: str, milestone_id: str, data: UpdateMilestone
+    ) -> Milestone:
+        """Update a milestone by ID.
+
+        Args:
+            workspace_slug: The workspace slug identifier
+            project_id: UUID of the project
+            milestone_id: UUID of the milestone
+            data: Updated milestone data
+        """
+        response = self._patch(
+            f"{workspace_slug}/projects/{project_id}/milestones/{milestone_id}",
+            data.model_dump(exclude_none=True),
+        )
+        return Milestone.model_validate(response)
+
+    def delete(self, workspace_slug: str, project_id: str, milestone_id: str) -> None:
+        """Delete a milestone by ID.
+
+        Args:
+            workspace_slug: The workspace slug identifier
+            project_id: UUID of the project
+            milestone_id: UUID of the milestone
+        """
+        return self._delete(f"{workspace_slug}/projects/{project_id}/milestones/{milestone_id}")
+
+    def list(
+        self, workspace_slug: str, project_id: str, params: Mapping[str, Any] | None = None
+    ) -> PaginatedMilestoneResponse:
+        """List milestones with optional filtering parameters.
+
+        Args:
+            workspace_slug: The workspace slug identifier
+            project_id: UUID of the project
+            params: Optional query parameters
+        """
+        response = self._get(f"{workspace_slug}/projects/{project_id}/milestones", params=params)
+        return PaginatedMilestoneResponse.model_validate(response)
+
+    def add_work_items(
+        self,
+        workspace_slug: str,
+        project_id: str,
+        milestone_id: str,
+        issue_ids: list[str],
+    ) -> None:
+        """Add work items to a milestone.
+
+        Args:
+            workspace_slug: The workspace slug identifier
+            project_id: UUID of the project
+            milestone_id: UUID of the milestone
+            issue_ids: List of issue IDs to add to the milestone
+        """
+        return self._post(
+            f"{workspace_slug}/projects/{project_id}/milestones/{milestone_id}/work-items",
+            {"issues": issue_ids},
+        )
+
+    def remove_work_items(
+        self,
+        workspace_slug: str,
+        project_id: str,
+        milestone_id: str,
+        issue_ids: list[str],
+    ) -> None:
+        """Remove work items from a milestone.
+
+        Args:
+            workspace_slug: The workspace slug identifier
+            project_id: UUID of the project
+            milestone_id: UUID of the milestone
+            issue_ids: List of issue IDs to remove from the milestone
+        """
+        return self._delete(
+            f"{workspace_slug}/projects/{project_id}/milestones/{milestone_id}/work-items",
+            {"issues": issue_ids},
+        )
+
+    def list_work_items(
+        self,
+        workspace_slug: str,
+        project_id: str,
+        milestone_id: str,
+        params: Mapping[str, Any] | None = None,
+    ) -> PaginatedMilestoneWorkItemResponse:
+        """List work items in a milestone.
+
+        Args:
+            workspace_slug: The workspace slug identifier
+            project_id: UUID of the project
+            milestone_id: UUID of the milestone
+            params: Optional query parameters
+        """
+        response = self._get(
+            f"{workspace_slug}/projects/{project_id}/milestones/{milestone_id}/work-items",
+            params=params,
+        )
+        return PaginatedMilestoneWorkItemResponse.model_validate(response)
diff --git a/plane/client/plane_client.py b/plane/client/plane_client.py
index a333fa3..581400c 100644
--- a/plane/client/plane_client.py
+++ b/plane/client/plane_client.py
@@ -5,6 +5,7 @@
 from ..api.initiatives import Initiatives
 from ..api.intake import Intake
 from ..api.labels import Labels
+from ..api.milestones import Milestones
 from ..api.modules import Modules
 from ..api.pages import Pages
 from ..api.projects import Projects
@@ -51,6 +52,7 @@ def __init__(
         self.pages = Pages(self.config)
         self.labels = Labels(self.config)
         self.states = States(self.config)
+        self.milestones = Milestones(self.config)
         self.modules = Modules(self.config)
         self.cycles = Cycles(self.config)
         self.work_item_types = WorkItemTypes(self.config)
diff --git a/plane/models/milestones.py b/plane/models/milestones.py
new file mode 100644
index 0000000..ce36008
--- /dev/null
+++ b/plane/models/milestones.py
@@ -0,0 +1,84 @@
+from typing import TYPE_CHECKING, Any
+
+from pydantic import BaseModel, ConfigDict
+
+from .pagination import PaginatedResponse
+
+if TYPE_CHECKING:
+    from .work_items import WorkItem
+
+
+class Milestone(BaseModel):
+    """Milestone model."""
+
+    model_config = ConfigDict(extra="allow", populate_by_name=True)
+
+    id: str | None = None
+    title: str
+    target_date: str | None = None
+    external_source: str | None = None
+    external_id: str | None = None
+    created_at: str | None = None
+    updated_at: str | None = None
+
+
+class MilestoneLite(BaseModel):
+    """Lite milestone information."""
+
+    model_config = ConfigDict(extra="allow", populate_by_name=True)
+
+    id: str | None = None
+    title: str
+    target_date: str | None = None
+    external_source: str | None = None
+    external_id: str | None = None
+    created_at: str | None = None
+    updated_at: str | None = None
+
+
+class CreateMilestone(BaseModel):
+    """Request model for creating a milestone."""
+
+    model_config = ConfigDict(extra="ignore", populate_by_name=True)
+
+    title: str
+    target_date: str | None = None
+    external_source: str | None = None
+    external_id: str | None = None
+
+
+class UpdateMilestone(BaseModel):
+    """Request model for updating a milestone."""
+
+    model_config = ConfigDict(extra="ignore", populate_by_name=True)
+
+    title: str | None = None
+    target_date: str | None = None
+    external_source: str | None = None
+    external_id: str | None = None
+
+
+class MilestoneWorkItem(BaseModel):
+    """Work item in a milestone."""
+
+    model_config = ConfigDict(extra="allow", populate_by_name=True)
+
+    id: str | None = None
+    issue: str | None = None
+    milestone: str | None = None
+
+
+class PaginatedMilestoneResponse(PaginatedResponse):
+    """Paginated response for milestones."""
+
+    model_config = ConfigDict(extra="allow", populate_by_name=True)
+
+    results: list[Milestone]
+
+
+class PaginatedMilestoneWorkItemResponse(PaginatedResponse):
+    """Paginated response for milestone work items."""
+
+    model_config = ConfigDict(extra="allow", populate_by_name=True)
+
+    results: list[MilestoneWorkItem]
diff --git a/tests/scripts/test_milestones.py b/tests/scripts/test_milestones.py
new file mode 100644
index 0000000..841fb15
--- /dev/null
+++ b/tests/scripts/test_milestones.py
@@ -0,0 +1,377 @@
+#!/usr/bin/env python3
+"""
+Comprehensive test script for testing SDK Milestone functionality end-to-end.
+
+This script demonstrates:
+1. Creating a project with milestone view enabled
+2. Creating work item types
+3. Creating multiple work items
+4. Creating multiple milestones
+5. Adding work items to milestones
+6. Updating milestone details
+7. Listing work items in a milestone
+8. Removing work items from a milestone
+
+Usage:
+    python test_milestones.py
+
+Requirements:
+    - Set PLANE_BASE_URL environment variable (e.g., https://api.plane.so)
+    - Set either PLANE_API_KEY or PLANE_ACCESS_TOKEN environment variable
+    - Set WORKSPACE_SLUG environment variable
+"""
+
+import os
+import sys
+from datetime import datetime, timedelta
+from pathlib import Path
+
+# Add project root to Python path
+project_root = Path(__file__).parent.parent.parent
+sys.path.insert(0, str(project_root))
+
+from plane.client import PlaneClient  # noqa: E402
+from plane.models.milestones import CreateMilestone, UpdateMilestone  # noqa: E402
+from plane.models.projects import CreateProject  # noqa: E402
+from plane.models.work_item_types import CreateWorkItemType  # noqa: E402
+from plane.models.work_items import CreateWorkItem  # noqa: E402
+
+
+def print_step(step_num: int, message: str) -> None:
+    """Print a formatted step message."""
+    print(f"\n{'=' * 70}")
+    print(f"Step {step_num}: {message}")
+    print("=" * 70)
+
+
+def print_success(message: str) -> None:
+    """Print a success message."""
+    print(f"✓ {message}")
+
+
+def print_error(message: str) -> None:
+    """Print an error message."""
+    print(f"✗ {message}", file=sys.stderr)
+
+
+def main() -> None:
+    """Main test function."""
+    # Get configuration from environment
+    base_url = os.getenv("PLANE_BASE_URL")
+    api_key = os.getenv("PLANE_API_KEY")
+    access_token = os.getenv("PLANE_ACCESS_TOKEN")
+    workspace_slug = os.getenv("WORKSPACE_SLUG")
+
+    # Validate required environment variables
+    if not base_url:
+        print_error("PLANE_BASE_URL environment variable is required")
+        sys.exit(1)
+
+    if not api_key and not access_token:
+        print_error("Either PLANE_API_KEY or PLANE_ACCESS_TOKEN environment variable is required")
+        sys.exit(1)
+
+    if not workspace_slug:
+        print_error("WORKSPACE_SLUG environment variable is required")
+        sys.exit(1)
+
+    print("Starting Milestone Test Suite")
+    print(f"Base URL: {base_url}")
+    print(f"Workspace: {workspace_slug}")
+    print(f"Authentication: {'API Key' if api_key else 'Access Token'}")
+
+    try:
+        # Initialize the client
+        print_step(1, "Initializing Plane Client")
+        client = PlaneClient(
+            base_url=base_url,
+            api_key=api_key,
+            access_token=access_token,
+        )
+        print_success("Client initialized successfully")
+
+        # Get current user for reference
+        print_step(2, "Getting current user information")
+        current_user = client.users.get_me()
+        print_success(f"Current user: {current_user.display_name} (ID: {current_user.id})")
+
+        # Create a project with milestone view enabled
+        print_step(3, "Creating a new project")
+        timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
+        project_identifier = f"MIL{timestamp[-6:]}"
+
+        project_data = CreateProject(
+            name=f"Milestone Test Project {timestamp}",
+            description="Testing milestone functionality end-to-end",
+            identifier=project_identifier,
+            emoji="🎯",
+        )
+
+        project = client.projects.create(workspace_slug, project_data)
+        print_success(f"Project created: {project.name} (ID: {project.id})")
+
+        # Create work item types
+        print_step(4, "Creating work item types")
+        work_item_types = {}
+
+        type_definitions = [
+            {
+                "key": "task",
+                "name": "Task",
+                "description": "A task to be completed",
+                "is_epic": False,
+            },
+            {
+                "key": "bug",
+                "name": "Bug",
+                "description": "A software bug that needs to be fixed",
+                "is_epic": False,
+            },
+        ]
+
+        for type_def in type_definitions:
+            type_data = CreateWorkItemType(
+                name=type_def["name"],
+                description=type_def["description"],
+                is_epic=type_def["is_epic"],
+                is_active=True,
+            )
+            work_item_type = client.work_item_types.create(workspace_slug, project.id, type_data)
+            work_item_types[type_def["key"]] = work_item_type
+            print_success(
+                f"Created work item type: {work_item_type.name} (ID: {work_item_type.id})"
+            )
+
+        # Create multiple work items
+        print_step(5, "Creating work items")
+        work_items = []
+
+        work_item_definitions = [
+            {
+                "name": "Implement core API endpoints",
+                "description": "Create REST API endpoints for core functionality",
+                "priority": "high",
+                "type_key": "task",
+            },
+            {
+                "name": "Design user interface mockups",
+                "description": "Design and document UI mockups",
+                "priority": "high",
+                "type_key": "task",
+            },
+            {
+                "name": "Setup testing framework",
+                "description": "Configure unit and integration testing",
+                "priority": "medium",
+                "type_key": "task",
+            },
+            {
+                "name": "Fix data validation issue",
+                "description": "Input data is not properly validated",
+                "priority": "high",
+                "type_key": "bug",
+            },
+            {
+                "name": "Fix performance bottleneck",
+                "description": "Slow response times on dashboard",
+                "priority": "urgent",
+                "type_key": "bug",
+            },
+        ]
+
+        for item_def in work_item_definitions:
+            work_item_data = CreateWorkItem(
+                name=item_def["name"],
+                description_html=f"<p>{item_def['description']}</p>",
+                priority=item_def["priority"],
+                type_id=work_item_types[item_def["type_key"]].id,
+            )
+            work_item = client.work_items.create(workspace_slug, project.id, work_item_data)
+            work_items.append(work_item)
+            print_success(f"Created work item: {work_item.name} (ID: {work_item.id})")
+
+        # Create multiple milestones
+        print_step(6, "Creating multiple milestones")
+        milestones = {}
+
+        # Milestone 1: v1.0 Release
+        v1_milestone_end = datetime.now() + timedelta(days=30)
+
+        v1_milestone_data = CreateMilestone(
+            title="v1.0 Release",
+            target_date=v1_milestone_end.strftime("%Y-%m-%d"),
+        )
+
+        milestones["v1"] = client.milestones.create(workspace_slug, project.id, v1_milestone_data)
+        print_success(f"Created milestone: {milestones['v1'].title} (ID: {milestones['v1'].id})")
+        print(f"  Target date: {milestones['v1'].target_date}")
+
+        # Milestone 2: v1.1 Release
+        v1_1_milestone_end = datetime.now() + timedelta(days=51)
+
+        v1_1_milestone_data = CreateMilestone(
+            title="v1.1 Release",
+            target_date=v1_1_milestone_end.strftime("%Y-%m-%d"),
+        )
+
+        milestones["v1_1"] = client.milestones.create(
+            workspace_slug, project.id, v1_1_milestone_data
+        )
+        print_success(f"Created milestone: {milestones['v1_1'].title} (ID: {milestones['v1_1'].id})")
+
+        # Milestone 3: v2.0 Release
+        v2_milestone_data = CreateMilestone(
+            title="v2.0 Release",
+        )
+
+        milestones["v2"] = client.milestones.create(workspace_slug, project.id, v2_milestone_data)
+        print_success(f"Created milestone: {milestones['v2'].title} (ID: {milestones['v2'].id})")
+
+        # Add work items to milestones
+        print_step(7, "Adding work items to milestones")
+
+        # Add core work items to v1.0 milestone
+        v1_work_item_ids = [work_items[0].id, work_items[1].id, work_items[3].id]
+        client.milestones.add_work_items(
+            workspace_slug, project.id, milestones["v1"].id, v1_work_item_ids
+        )
+        print_success(f"Added {len(v1_work_item_ids)} work items to {milestones['v1'].title}")
+
+        # Add testing work item to v1.1 milestone
+        v1_1_work_item_ids = [work_items[2].id]
+        client.milestones.add_work_items(
+            workspace_slug, project.id, milestones["v1_1"].id, v1_1_work_item_ids
+        )
+        print_success(f"Added {len(v1_1_work_item_ids)} work item to {milestones['v1_1'].title}")
+
+        # Add critical bug to v1.0 milestone
+        critical_bug_ids = [work_items[4].id]
+        client.milestones.add_work_items(
+            workspace_slug, project.id, milestones["v1"].id, critical_bug_ids
+        )
+        print_success(f"Added critical bug to {milestones['v1'].title}")
+
+        # List work items in milestones
+        print_step(8, "Listing work items in milestones")
+
+        for _, milestone in milestones.items():
+            milestone_work_items = client.milestones.list_work_items(
+                workspace_slug, project.id, milestone.id
+            )
+            print_success(f"{milestone.title} contains {milestone_work_items.count} work items")
+
+        # Update milestone details
+        print_step(9, "Updating milestone details")
+
+        # Update v1.0 milestone title
+        update_v1_data = UpdateMilestone(
+            title="v1.0 Release - Updated",
+        )
+        updated_v1_milestone = client.milestones.update(
+            workspace_slug, project.id, milestones["v1"].id, update_v1_data
+        )
+        print_success(f"Updated milestone title to: {updated_v1_milestone.title}")
+
+        # Update v1.1 milestone target date
+        new_v1_1_end = datetime.now() + timedelta(days=49)
+        update_v1_1_data = UpdateMilestone(
+            target_date=new_v1_1_end.strftime("%Y-%m-%d"),
+        )
+        updated_v1_1_milestone = client.milestones.update(
+            workspace_slug, project.id, milestones["v1_1"].id, update_v1_1_data
+        )
+        print_success(f"Updated {updated_v1_1_milestone.title} target date")
+        print(f"  New target date: {updated_v1_1_milestone.target_date}")
+
+        # Retrieve a specific milestone
+        print_step(10, "Retrieving specific milestone")
+        retrieved_milestone = client.milestones.retrieve(
+            workspace_slug, project.id, milestones["v1"].id
+        )
+        print_success(f"Retrieved milestone: {retrieved_milestone.title}")
+
+        # List all milestones in project
+        print_step(11, "Listing all milestones in project")
+        all_milestones = client.milestones.list(workspace_slug, project.id)
+        print_success(f"Found {all_milestones.count} milestones in project")
+        for milestone in all_milestones.results:
+            print(f"  - {milestone.title}")
+
+        # Remove work items from a milestone
+        print_step(12, "Removing work item from milestone")
+        work_item_to_remove = [work_items[3].id]  # Data validation bug
+        client.milestones.remove_work_items(
+            workspace_slug, project.id, milestones["v1"].id, work_item_to_remove
+        )
+        print_success(f"Removed work item '{work_items[3].name}' from {milestones['v1'].title}")
+
+        # Verify removal
+        v1_work_items_after_removal = client.milestones.list_work_items(
+            workspace_slug, project.id, milestones["v1"].id
+        )
+        print_success(
+            f"{milestones['v1'].title} now contains "
+            f"{v1_work_items_after_removal.count} work items"
+        )
+
+        # Final milestone count
+        print_step(13, "Final verification")
+        final_milestones = client.milestones.list(workspace_slug, project.id)
+        print_success(f"Total milestones: {final_milestones.count}")
+
+        # Cleanup: Delete created resources (optional)
+        print_step(14, "Cleanup (optional)")
+        try:
+            choice = input("Delete test resources? (y/N): ").strip().lower()
+        except EOFError:
+            choice = "n"
+        if choice == "y":
+            # Delete milestones
+            for milestone in milestones.values():
+                try:
+                    client.milestones.delete(workspace_slug, project.id, milestone.id)
+                    print_success(f"Deleted milestone: {milestone.title}")
+                except Exception as e:
+                    print_error(f"Failed to delete milestone {milestone.id}: {e}")
+
+            # Delete work items
+            for work_item in work_items:
+                try:
+                    client.work_items.delete(workspace_slug, project.id, work_item.id)
+                    print_success(f"Deleted work item: {work_item.id}")
+                except Exception as e:
+                    print_error(f"Failed to delete work item {work_item.id}: {e}")
+
+            # Delete project
+            try:
+                client.projects.delete(workspace_slug, project.id)
+                print_success("Deleted test project")
+            except Exception as e:
+                print_error(f"Failed to delete project: {e}")
+        else:
+            print_success("Keeping test resources for inspection")
+
+        # Summary
+        print_step(15, "Test Summary")
+        print(f"✓ Project created: {project.name}")
+        print(f"✓ Work item types created: {len(work_item_types)}")
+        print(f"✓ Work items created: {len(work_items)}")
+        print(f"✓ Milestones created: {len(milestones)}")
+        print("✓ Work items added to milestones")
+        print("✓ Work items removed from milestones")
+        print("✓ Milestones updated (title, target date)")
+        print("✓ Milestone retrieved successfully")
+        print("✓ Milestones listed successfully")
+        print("\nAll milestone tests completed successfully!")
+        print(f"\nView your project at: {base_url}/w/{workspace_slug}/p/{project.id}")
+
+    except Exception as e:
+        print_error(f"Test failed with error: {e}")
+        import traceback
+
+        traceback.print_exc()
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/tests/unit/test_milestones.py b/tests/unit/test_milestones.py
new file mode 100644
index 0000000..5cb82e6
--- /dev/null
+++ b/tests/unit/test_milestones.py
@@ -0,0 +1,103 @@
+"""Unit tests for Milestones API resource (smoke tests with real HTTP requests)."""
+
+from datetime import datetime
+
+import pytest
+
+from plane.client import PlaneClient
+from plane.models.milestones import CreateMilestone, UpdateMilestone
+from plane.models.projects import Project, ProjectFeature
+
+
+class TestMilestonesAPI:
+    """Test Milestones API resource."""
+
+    def test_list_milestones(
+        self, client: PlaneClient, workspace_slug: str, project: Project
+    ) -> None:
+        """Test listing milestones."""
+        response = client.milestones.list(workspace_slug, project.id)
+        assert response is not None
+        assert hasattr(response, "results")
+        assert hasattr(response, "count")
+        assert isinstance(response.results, list)
+
+
+class TestMilestonesAPICRUD:
+    """Test Milestones API CRUD operations."""
+
+    @pytest.fixture
+    def milestone_data(self) -> CreateMilestone:
+        """Create test milestone data."""
+        import time
+        end_date = datetime.now()
+        return CreateMilestone(
+            title=f"Test Milestone {int(time.time())}",
+            target_date=end_date.strftime("%Y-%m-%d"),
+        )
+
+    @pytest.fixture
+    def milestone(
+        self,
+        client: PlaneClient,
+        workspace_slug: str,
+        project: Project,
+        milestone_data: CreateMilestone,
+    ):
+        """Create a test milestone and yield it, then delete it."""
+        client.projects.update_features(workspace_slug, project.id, ProjectFeature(modules=True))
+        milestone = client.milestones.create(workspace_slug, project.id, milestone_data)
+        yield milestone
+        try:
+            client.milestones.delete(workspace_slug, project.id, milestone.id)
+        except Exception:
+            pass
+
+    def test_create_milestone(
+        self,
+        client: PlaneClient,
+        workspace_slug: str,
+        project: Project,
+        milestone_data: CreateMilestone,
+    ) -> None:
+        """Test creating a milestone."""
+        client.projects.update_features(workspace_slug, project.id, ProjectFeature(modules=True))
+        milestone = client.milestones.create(workspace_slug, project.id, milestone_data)
+        assert milestone is not None
+        assert milestone.id is not None
+        assert milestone.title == milestone_data.title
+
+        # Cleanup
+        try:
+            client.milestones.delete(workspace_slug, project.id, milestone.id)
+        except Exception:
+            pass
+
+    def test_retrieve_milestone(
+        self, client: PlaneClient, workspace_slug: str, project: Project, milestone
+    ) -> None:
+        """Test retrieving a milestone."""
+        retrieved = client.milestones.retrieve(workspace_slug, project.id, milestone.id)
+        assert retrieved is not None
+        assert retrieved.id == milestone.id
+        assert retrieved.title == milestone.title
+
+    def test_update_milestone(
+        self, client: PlaneClient, workspace_slug: str, project: Project, milestone
+    ) -> None:
+        """Test updating a milestone."""
+        update_data = UpdateMilestone(title="Updated Milestone Title")
+        updated = client.milestones.update(workspace_slug, project.id, milestone.id, update_data)
+        assert updated is not None
+        assert updated.id == milestone.id
+        assert updated.title == "Updated Milestone Title"
+
+    def test_list_work_items(
+        self, client: PlaneClient, workspace_slug: str, project: Project, milestone
+    ) -> None:
+        """Test listing work items in a milestone."""
+        response = client.milestones.list_work_items(workspace_slug, project.id, milestone.id)
+        assert response is not None
+        assert hasattr(response, "results")
+        assert hasattr(response, "count")
+        assert isinstance(response.results, list)