diff --git a/src/api/Milestones.ts b/src/api/Milestones.ts
new file mode 100644
index 0000000..af2fcc2
--- /dev/null
+++ b/src/api/Milestones.ts
@@ -0,0 +1,99 @@
+import { BaseResource } from "./BaseResource";
+import { Configuration } from "../Configuration";
+import { PaginatedResponse } from "../models/common";
+
+import { Milestone, CreateMilestoneRequest, UpdateMilestoneRequest, MilestoneWorkItem } from "../models/Milestone";
+
+/**
+ * Milestones API resource
+ * Handles all milestone related operations
+ */
+export class Milestones extends BaseResource {
+  constructor(config: Configuration) {
+    super(config);
+  }
+
+  /**
+   * Create a new milestone
+   */
+  async create(workspaceSlug: string, projectId: string, createMilestone: CreateMilestoneRequest): Promise<Milestone> {
+    return this.post<Milestone>(`/workspaces/${workspaceSlug}/projects/${projectId}/milestones/`, createMilestone);
+  }
+
+  /**
+   * Retrieve a milestone by ID
+   */
+  async retrieve(workspaceSlug: string, projectId: string, milestoneId: string): Promise<Milestone> {
+    return this.get<Milestone>(`/workspaces/${workspaceSlug}/projects/${projectId}/milestones/${milestoneId}/`);
+  }
+
+  /**
+   * Update a milestone
+   */
+  async update(
+    workspaceSlug: string,
+    projectId: string,
+    milestoneId: string,
+    updateMilestone: UpdateMilestoneRequest
+  ): Promise<Milestone> {
+    return this.patch<Milestone>(
+      `/workspaces/${workspaceSlug}/projects/${projectId}/milestones/${milestoneId}/`,
+      updateMilestone
+    );
+  }
+
+  /**
+   * Delete a milestone
+   */
+  async delete(workspaceSlug: string, projectId: string, milestoneId: string): Promise<void> {
+    return this.httpDelete(`/workspaces/${workspaceSlug}/projects/${projectId}/milestones/${milestoneId}/`);
+  }
+
+  /**
+   * List milestones with optional filtering
+   */
+  async list(workspaceSlug: string, projectId: string, params?: any): Promise<PaginatedResponse<Milestone>> {
+    return this.get<PaginatedResponse<Milestone>>(
+      `/workspaces/${workspaceSlug}/projects/${projectId}/milestones/`,
+      params
+    );
+  }
+
+  /**
+   * Add work items to a milestone
+   */
+  async addWorkItems(workspaceSlug: string, projectId: string, milestoneId: string, issueIds: string[]): Promise<void> {
+    return this.post<void>(`/workspaces/${workspaceSlug}/projects/${projectId}/milestones/${milestoneId}/work-items/`, {
+      issues: issueIds,
+    });
+  }
+
+  /**
+   * Remove work items from a milestone
+   */
+  async removeWorkItems(
+    workspaceSlug: string,
+    projectId: string,
+    milestoneId: string,
+    issueIds: string[]
+  ): Promise<void> {
+    return this.httpDelete(`/workspaces/${workspaceSlug}/projects/${projectId}/milestones/${milestoneId}/work-items/`, {
+      issues: issueIds,
+    });
+  }
+
+  /**
+   * List work items in a milestone
+   */
+  async listWorkItems(
+    workspaceSlug: string,
+    projectId: string,
+    milestoneId: string,
+    params?: any
+  ): Promise<PaginatedResponse<MilestoneWorkItem>> {
+    return this.get<PaginatedResponse<MilestoneWorkItem>>(
+      `/workspaces/${workspaceSlug}/projects/${projectId}/milestones/${milestoneId}/work-items/`,
+      params
+    );
+  }
+}
diff --git a/src/client/plane-client.ts b/src/client/plane-client.ts
index 3ab76e6..8245222 100644
--- a/src/client/plane-client.ts
+++ b/src/client/plane-client.ts
@@ -18,6 +18,7 @@ import { Intake } from "../api/Intake";
 import { Stickies } from "../api/Stickies";
 import { Teamspaces } from "../api/Teamspaces";
 import { Initiatives } from "../api/Initiatives";
+import { Milestones } from "../api/Milestones";
 import { AgentRuns } from "../api/AgentRuns";
 
 /**
@@ -44,6 +45,7 @@ export class PlaneClient {
   public intake: Intake;
   public stickies: Stickies;
   public teamspaces: Teamspaces;
+  public milestones: Milestones;
   public initiatives: Initiatives;
   public agentRuns: AgentRuns;
 
@@ -77,6 +79,7 @@ export class PlaneClient {
     this.intake = new Intake(this.config);
     this.stickies = new Stickies(this.config);
     this.teamspaces = new Teamspaces(this.config);
+    this.milestones = new Milestones(this.config);
     this.initiatives = new Initiatives(this.config);
     this.agentRuns = new AgentRuns(this.config);
   }
diff --git a/src/index.ts b/src/index.ts
index 151bd76..4b17201 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -29,6 +29,7 @@ export { Epics } from "./api/Epics";
 export { Intake } from "./api/Intake";
 export { Stickies } from "./api/Stickies";
 export { Teamspaces } from "./api/Teamspaces";
+export { Milestones } from "./api/Milestones";
 export { Initiatives } from "./api/Initiatives";
 export { AgentRuns } from "./api/AgentRuns";
 
diff --git a/src/models/Milestone.ts b/src/models/Milestone.ts
new file mode 100644
index 0000000..bbeded9
--- /dev/null
+++ b/src/models/Milestone.ts
@@ -0,0 +1,42 @@
+import { BaseModel } from "./common";
+
+export interface Milestone extends BaseModel {
+  title: string;
+  // YYYY-MM-DD format
+  target_date?: string;
+  project: string;
+  workspace: string;
+}
+
+export interface MilestoneLite {
+  id?: string;
+  title: string;
+  // YYYY-MM-DD format
+  target_date?: string;
+  external_source?: string;
+  external_id?: string;
+  created_at?: string;
+  updated_at?: string;
+}
+
+export interface CreateMilestoneRequest {
+  title: string;
+  // YYYY-MM-DD format
+  target_date?: string;
+  external_source?: string;
+  external_id?: string;
+}
+
+export interface UpdateMilestoneRequest {
+  title?: string;
+  // YYYY-MM-DD format
+  target_date?: string;
+  external_source?: string;
+  external_id?: string;
+}
+
+export interface MilestoneWorkItem {
+  id?: string;
+  issue?: string;
+  milestone?: string;
+}
diff --git a/src/models/index.ts b/src/models/index.ts
index 9abbc19..ce61a01 100644
--- a/src/models/index.ts
+++ b/src/models/index.ts
@@ -10,6 +10,7 @@ export * from "./InitiativeLabel";
 export * from "./Intake";
 export * from "./Label";
 export * from "./Link";
+export * from "./Milestone";
 export * from "./Module";
 export * from "./OAuth";
 export * from "./Page";
diff --git a/tests/unit/milestone.test.ts b/tests/unit/milestone.test.ts
new file mode 100644
index 0000000..b944b34
--- /dev/null
+++ b/tests/unit/milestone.test.ts
@@ -0,0 +1,125 @@
+import { PlaneClient } from "../../src/client/plane-client";
+import { Milestone, UpdateMilestoneRequest, MilestoneWorkItem } from "../../src/models";
+import { config } from "./constants";
+import { createTestClient } from "../helpers/test-utils";
+import { describeIf as describe } from "../helpers/conditional-tests";
+
+describe(!!(config.workspaceSlug && config.projectId && config.workItemId), "Milestone API Tests", () => {
+  let client: PlaneClient;
+  let workspaceSlug: string;
+  let projectId: string;
+  let workItemId: string;
+  let milestone: Milestone;
+
+  beforeAll(async () => {
+    client = createTestClient();
+    workspaceSlug = config.workspaceSlug;
+    projectId = config.projectId;
+    workItemId = config.workItemId;
+  });
+
+  afterAll(async () => {
+    // Clean up created resources
+    if (milestone?.id) {
+      try {
+        await client.milestones.delete(workspaceSlug, projectId, milestone.id);
+      } catch (error) {
+        console.warn("Failed to delete milestone:", error);
+      }
+    }
+  });
+
+  it("should create a milestone", async () => {
+    milestone = await client.milestones.create(workspaceSlug, projectId, {
+      title: "Test Milestone",
+    });
+
+    expect(milestone).toBeDefined();
+    expect(milestone.id).toBeDefined();
+    expect(milestone.title).toBe("Test Milestone");
+  });
+
+  it("should retrieve a milestone", async () => {
+    const retrievedMilestone = await client.milestones.retrieve(workspaceSlug, projectId, milestone.id);
+
+    expect(retrievedMilestone).toBeDefined();
+    expect(retrievedMilestone.id).toBe(milestone.id);
+    expect(retrievedMilestone.title).toBe(milestone.title);
+  });
+
+  it("should update a milestone", async () => {
+    const updateData: UpdateMilestoneRequest = {
+      title: "Updated Test Milestone",
+      target_date: "2026-12-31",
+    };
+
+    const updatedMilestone = await client.milestones.update(
+      workspaceSlug,
+      projectId,
+      milestone.id,
+      updateData
+    );
+
+    expect(updatedMilestone).toBeDefined();
+    expect(updatedMilestone.id).toBe(milestone.id);
+    expect(updatedMilestone.title).toBe("Updated Test Milestone");
+    expect(updatedMilestone.target_date).toBe("2026-12-31");
+  });
+
+  it("should list milestones", async () => {
+    const milestones = await client.milestones.list(workspaceSlug, projectId);
+
+    expect(milestones).toBeDefined();
+    expect(Array.isArray(milestones.results)).toBe(true);
+    expect(milestones.results.length).toBeGreaterThan(0);
+
+    const foundMilestone = milestones.results.find((m) => m.id === milestone.id);
+    expect(foundMilestone).toBeDefined();
+    expect(foundMilestone?.title).toBe("Updated Test Milestone");
+  });
+
+  it("should add work items to milestone", async () => {
+    await client.milestones.addWorkItems(workspaceSlug, projectId, milestone.id, [workItemId]);
+
+    const workItems = await client.milestones.listWorkItems(workspaceSlug, projectId, milestone.id);
+
+    expect(workItems).toBeDefined();
+    expect(Array.isArray(workItems.results)).toBe(true);
+    expect(workItems.results.length).toBeGreaterThan(0);
+  });
+
+  it("should list work items in milestone", async () => {
+    const workItems = await client.milestones.listWorkItems(workspaceSlug, projectId, milestone.id);
+
+    expect(workItems).toBeDefined();
+    expect(Array.isArray(workItems.results)).toBe(true);
+    expect(workItems.results.length).toBeGreaterThan(0);
+  });
+
+  it("should remove work items from milestone", async () => {
+    await client.milestones.removeWorkItems(workspaceSlug, projectId, milestone.id, [workItemId]);
+
+    const workItems = await client.milestones.listWorkItems(workspaceSlug, projectId, milestone.id);
+
+    expect(workItems).toBeDefined();
+    expect(Array.isArray(workItems.results)).toBe(true);
+
+    const foundWorkItem = workItems.results.find((item: MilestoneWorkItem) => item.issue === workItemId);
+    expect(foundWorkItem).toBeUndefined();
+  });
+
+  it("should delete a milestone", async () => {
+    await client.milestones.delete(workspaceSlug, projectId, milestone.id);
+
+    // Verify it's deleted by trying to retrieve it
+    try {
+      await client.milestones.retrieve(workspaceSlug, projectId, milestone.id);
+      fail("Expected an error when retrieving a deleted milestone");
+    } catch (error) {
+      expect(error).toBeDefined();
+    }
+
+    // Prevent afterAll from trying to delete again
+    milestone = undefined as any;
+  });
+});