diff --git a/packages/mcp/src/functions/delete-session.ts b/packages/mcp/src/functions/delete-session.ts
new file mode 100644
index 0000000..9fa4603
--- /dev/null
+++ b/packages/mcp/src/functions/delete-session.ts
@@ -0,0 +1,129 @@
+import type { JulesClient } from '@google/jules-sdk';
+import type { DeleteSessionOptions, DeleteSessionResult } from './types.js';
+
+/**
+ * Deletes sessions by ID or filter.
+ *
+ * @param client - The Jules client instance
+ * @param options - Deletion options (sessionId, filter, force)
+ * @returns Deletion result
+ */
+export async function deleteSession(
+  client: JulesClient,
+  options: DeleteSessionOptions,
+): Promise<DeleteSessionResult> {
+  const { sessionId, filter, force } = options;
+
+  if (sessionId) {
+    try {
+      await client.session(sessionId).delete();
+      return {
+        success: true,
+        deletedCount: 1,
+        sessionIds: [sessionId],
+        message: `Session ${sessionId} deleted successfully.`,
+      };
+    } catch (error: any) {
+      return {
+        success: false,
+        deletedCount: 0,
+        sessionIds: [],
+        message: `Failed to delete session ${sessionId}: ${error.message}`,
+      };
+    }
+  }
+
+  if (filter) {
+    const sessionsToDelete: string[] = [];
+
+    // Iterate through all sessions to find matches.
+    // By default client.sessions() excludes archived sessions, which is usually desired.
+    for await (const session of client.sessions()) {
+      let match = false;
+      switch (filter) {
+        case 'completed':
+          match = session.state === 'completed';
+          break;
+        case 'failed':
+          match = session.state === 'failed';
+          break;
+        case 'running':
+          match = [
+            'queued',
+            'planning',
+            'inProgress',
+            'awaitingPlanApproval',
+            'awaitingUserFeedback',
+            'paused',
+          ].includes(session.state);
+          break;
+        case 'queued':
+          match = session.state === 'queued';
+          break;
+        case 'planning':
+          match = session.state === 'planning';
+          break;
+        case 'inProgress':
+          match = session.state === 'inProgress';
+          break;
+        case 'awaitingPlanApproval':
+          match = session.state === 'awaitingPlanApproval';
+          break;
+      }
+
+      if (match) {
+        sessionsToDelete.push(session.id);
+      }
+    }
+
+    if (sessionsToDelete.length === 0) {
+      return {
+        success: true,
+        deletedCount: 0,
+        sessionIds: [],
+        message: `No sessions found matching filter: ${filter}`,
+      };
+    }
+
+    if (!force) {
+      return {
+        success: false,
+        deletedCount: 0,
+        sessionIds: sessionsToDelete,
+        message: `Found ${sessionsToDelete.length} sessions matching filter "${filter}". Use 'force: true' to delete them.`,
+        requiresForce: true,
+      };
+    }
+
+    const deletedIds: string[] = [];
+    const errors: string[] = [];
+
+    // Delete in parallel with some concurrency or sequentially?
+    // Let's go with sequential for safety or use a simple loop.
+    for (const id of sessionsToDelete) {
+      try {
+        await client.session(id).delete();
+        deletedIds.push(id);
+      } catch (error: any) {
+        errors.push(`Failed to delete session ${id}: ${error.message}`);
+      }
+    }
+
+    return {
+      success: errors.length === 0,
+      deletedCount: deletedIds.length,
+      sessionIds: deletedIds,
+      message:
+        errors.length === 0
+          ? `Successfully deleted ${deletedIds.length} sessions matching filter "${filter}".`
+          : `Deleted ${deletedIds.length} sessions with ${errors.length} errors. Errors: ${errors.join('; ')}`,
+    };
+  }
+
+  return {
+    success: false,
+    deletedCount: 0,
+    sessionIds: [],
+    message: 'Either sessionId or filter must be provided.',
+  };
+}
diff --git a/packages/mcp/src/functions/index.ts b/packages/mcp/src/functions/index.ts
index 37f705a..e2694ff 100644
--- a/packages/mcp/src/functions/index.ts
+++ b/packages/mcp/src/functions/index.ts
@@ -6,6 +6,7 @@
 // Export all functions
 export { getSessionState } from './session-state.js';
 export { listSessions } from './list-sessions.js';
+export { deleteSession } from './delete-session.js';
 export { createSession } from './create-session.js';
 export { interact } from './interact.js';
 export { select } from './select.js';
@@ -27,6 +28,10 @@ export type {
   // List Sessions
   ListSessionsOptions,
   ListSessionsResult,
+  // Delete Session
+  DeleteSessionFilter,
+  DeleteSessionOptions,
+  DeleteSessionResult,
   // Create Session
   CreateSessionOptions,
   CreateSessionResult,
diff --git a/packages/mcp/src/functions/types.ts b/packages/mcp/src/functions/types.ts
index 9e378fb..1c6019d 100644
--- a/packages/mcp/src/functions/types.ts
+++ b/packages/mcp/src/functions/types.ts
@@ -327,3 +327,33 @@ export interface WorkInProgressResult {
   summary: WorkInProgressSummary;
   formatted: string;
 }
+
+// ============================================================================
+// Delete Session
+// ============================================================================
+
+export type DeleteSessionFilter =
+  | 'completed'
+  | 'failed'
+  | 'running'
+  | 'queued'
+  | 'planning'
+  | 'inProgress'
+  | 'awaitingPlanApproval';
+
+export interface DeleteSessionOptions {
+  sessionId?: string;
+  filter?: DeleteSessionFilter;
+  /**
+   * Required when deleting multiple sessions via filter.
+   */
+  force?: boolean;
+}
+
+export interface DeleteSessionResult {
+  success: boolean;
+  deletedCount: number;
+  sessionIds: string[];
+  message: string;
+  requiresForce?: boolean;
+}
diff --git a/packages/mcp/src/tools/delete-session.tool.ts b/packages/mcp/src/tools/delete-session.tool.ts
new file mode 100644
index 0000000..b914e5a
--- /dev/null
+++ b/packages/mcp/src/tools/delete-session.tool.ts
@@ -0,0 +1,42 @@
+import type { JulesClient } from '@google/jules-sdk';
+import { deleteSession } from '../functions/delete-session.js';
+import { defineTool, toMcpResponse } from './utils.js';
+
+export default defineTool({
+  name: 'delete_session',
+  description: 'Deletes one or more Jules sessions.',
+  inputSchema: {
+    type: 'object',
+    properties: {
+      sessionId: {
+        type: 'string',
+        description: 'The unique ID of the session to delete.',
+      },
+      filter: {
+        type: 'string',
+        description: 'A filter to delete multiple sessions.',
+        enum: [
+          'completed',
+          'failed',
+          'running',
+          'queued',
+          'planning',
+          'inProgress',
+          'awaitingPlanApproval',
+        ],
+      },
+      force: {
+        type: 'boolean',
+        description: 'Required when deleting multiple sessions via filter.',
+      },
+    },
+  },
+  handler: async (client: JulesClient, args: any) => {
+    const result = await deleteSession(client, {
+      sessionId: args?.sessionId,
+      filter: args?.filter,
+      force: args?.force,
+    });
+    return toMcpResponse(result);
+  },
+});
diff --git a/packages/mcp/tests/functions/delete-session.test.ts b/packages/mcp/tests/functions/delete-session.test.ts
new file mode 100644
index 0000000..77f319b
--- /dev/null
+++ b/packages/mcp/tests/functions/delete-session.test.ts
@@ -0,0 +1,128 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { deleteSession } from '../../src/functions/delete-session.js';
+import { createMockClient } from './helpers.js';
+
+describe('deleteSession', () => {
+  let mockClient: ReturnType<typeof createMockClient>;
+
+  beforeEach(() => {
+    mockClient = createMockClient();
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it('deletes a single session by ID', async () => {
+    const mockSession = {
+      delete: vi.fn().mockResolvedValue(undefined),
+    };
+    vi.spyOn(mockClient, 'session').mockReturnValue(mockSession as any);
+
+    const result = await deleteSession(mockClient, { sessionId: 'session-123' });
+
+    expect(result.success).toBe(true);
+    expect(result.deletedCount).toBe(1);
+    expect(result.sessionIds).toEqual(['session-123']);
+    expect(mockSession.delete).toHaveBeenCalled();
+  });
+
+  it('fails when single session deletion fails', async () => {
+    const mockSession = {
+      delete: vi.fn().mockRejectedValue(new Error('API Error')),
+    };
+    vi.spyOn(mockClient, 'session').mockReturnValue(mockSession as any);
+
+    const result = await deleteSession(mockClient, { sessionId: 'session-123' });
+
+    expect(result.success).toBe(false);
+    expect(result.deletedCount).toBe(0);
+    expect(result.message).toContain('Failed to delete session session-123');
+  });
+
+  it('deletes multiple sessions with filter and force', async () => {
+    const sessions = [
+      { id: 's1', state: 'completed' },
+      { id: 's2', state: 'failed' },
+      { id: 's3', state: 'completed' },
+    ];
+
+    vi.spyOn(mockClient, 'sessions').mockReturnValue({
+      [Symbol.asyncIterator]: async function* () {
+        for (const s of sessions) yield s;
+      },
+    } as any);
+
+    const mockDelete = vi.fn().mockResolvedValue(undefined);
+    vi.spyOn(mockClient, 'session').mockReturnValue({
+      delete: mockDelete,
+    } as any);
+
+    const result = await deleteSession(mockClient, {
+      filter: 'completed',
+      force: true,
+    });
+
+    expect(result.success).toBe(true);
+    expect(result.deletedCount).toBe(2);
+    expect(result.sessionIds).toEqual(['s1', 's3']);
+    expect(mockDelete).toHaveBeenCalledTimes(2);
+  });
+
+  it('requires force for multiple sessions', async () => {
+    const sessions = [{ id: 's1', state: 'completed' }];
+
+    vi.spyOn(mockClient, 'sessions').mockReturnValue({
+      [Symbol.asyncIterator]: async function* () {
+        for (const s of sessions) yield s;
+      },
+    } as any);
+
+    const result = await deleteSession(mockClient, { filter: 'completed' });
+
+    expect(result.success).toBe(false);
+    expect(result.requiresForce).toBe(true);
+    expect(result.sessionIds).toEqual(['s1']);
+  });
+
+  it('handles running filter correctly', async () => {
+    const sessions = [
+      { id: 's1', state: 'inProgress' },
+      { id: 's2', state: 'completed' },
+      { id: 's3', state: 'queued' },
+    ];
+
+    vi.spyOn(mockClient, 'sessions').mockReturnValue({
+      [Symbol.asyncIterator]: async function* () {
+        for (const s of sessions) yield s;
+      },
+    } as any);
+
+    const mockDelete = vi.fn().mockResolvedValue(undefined);
+    vi.spyOn(mockClient, 'session').mockReturnValue({
+      delete: mockDelete,
+    } as any);
+
+    const result = await deleteSession(mockClient, {
+      filter: 'running',
+      force: true,
+    });
+
+    expect(result.deletedCount).toBe(2);
+    expect(result.sessionIds).toEqual(['s1', 's3']);
+  });
+
+  it('returns success when no sessions match filter', async () => {
+    vi.spyOn(mockClient, 'sessions').mockReturnValue({
+      [Symbol.asyncIterator]: async function* () {
+        // empty
+      },
+    } as any);
+
+    const result = await deleteSession(mockClient, { filter: 'completed' });
+
+    expect(result.success).toBe(true);
+    expect(result.deletedCount).toBe(0);
+    expect(result.message).toContain('No sessions found matching filter');
+  });
+});