diff --git a/tests/integration/n8n-api/utils/node-repository.ts b/tests/integration/n8n-api/utils/node-repository.ts
new file mode 100644
index 0000000..e11ca41
--- /dev/null
+++ b/tests/integration/n8n-api/utils/node-repository.ts
@@ -0,0 +1,35 @@
+/**
+ * Node Repository Utility for Integration Tests
+ *
+ * Provides a singleton NodeRepository instance for integration tests
+ * that require validation or autofix functionality.
+ */
+
+import path from 'path';
+import { createDatabaseAdapter } from '../../../../src/database/database-adapter';
+import { NodeRepository } from '../../../../src/database/node-repository';
+
+let repositoryInstance: NodeRepository | null = null;
+
+/**
+ * Get or create NodeRepository instance
+ * Uses the production nodes.db database
+ */
+export async function getNodeRepository(): Promise<NodeRepository> {
+  if (repositoryInstance) {
+    return repositoryInstance;
+  }
+
+  const dbPath = path.join(process.cwd(), 'data/nodes.db');
+  const db = await createDatabaseAdapter(dbPath);
+  repositoryInstance = new NodeRepository(db);
+
+  return repositoryInstance;
+}
+
+/**
+ * Reset repository instance (useful for test cleanup)
+ */
+export function resetNodeRepository(): void {
+  repositoryInstance = null;
+}
diff --git a/tests/integration/n8n-api/workflows/validate-workflow.test.ts b/tests/integration/n8n-api/workflows/validate-workflow.test.ts
new file mode 100644
index 0000000..4aeb101
--- /dev/null
+++ b/tests/integration/n8n-api/workflows/validate-workflow.test.ts
@@ -0,0 +1,430 @@
+/**
+ * Integration Tests: handleValidateWorkflow
+ *
+ * Tests workflow validation against a real n8n instance.
+ * Covers validation profiles, validation types, and error detection.
+ */
+
+import { describe, it, expect, beforeEach, afterEach, afterAll } from 'vitest';
+import { createTestContext, TestContext, createTestWorkflowName } from '../utils/test-context';
+import { getTestN8nClient } from '../utils/n8n-client';
+import { N8nApiClient } from '../../../../src/services/n8n-api-client';
+import { SIMPLE_WEBHOOK_WORKFLOW } from '../utils/fixtures';
+import { cleanupOrphanedWorkflows } from '../utils/cleanup-helpers';
+import { createMcpContext } from '../utils/mcp-context';
+import { InstanceContext } from '../../../../src/types/instance-context';
+import { handleValidateWorkflow } from '../../../../src/mcp/handlers-n8n-manager';
+import { getNodeRepository } from '../utils/node-repository';
+import { NodeRepository } from '../../../../src/database/node-repository';
+
+describe('Integration: handleValidateWorkflow', () => {
+  let context: TestContext;
+  let client: N8nApiClient;
+  let mcpContext: InstanceContext;
+  let repository: NodeRepository;
+
+  beforeEach(async () => {
+    context = createTestContext();
+    client = getTestN8nClient();
+    mcpContext = createMcpContext();
+    repository = await getNodeRepository();
+  });
+
+  afterEach(async () => {
+    await context.cleanup();
+  });
+
+  afterAll(async () => {
+    if (!process.env.CI) {
+      await cleanupOrphanedWorkflows();
+    }
+  });
+
+  // ======================================================================
+  // Valid Workflow - All Profiles
+  // ======================================================================
+
+  describe('Valid Workflow', () => {
+    it('should validate valid workflow with default profile (runtime)', async () => {
+      // Create valid workflow
+      const workflow = {
+        ...SIMPLE_WEBHOOK_WORKFLOW,
+        name: createTestWorkflowName('Validate - Valid Default'),
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      // Validate with default profile
+      const response = await handleValidateWorkflow(
+        { id: created.id },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+
+      // Verify response structure
+      expect(data.valid).toBe(true);
+      expect(data.errors).toBeUndefined(); // Only present if errors exist
+      expect(data.summary).toBeDefined();
+      expect(data.summary.errorCount).toBe(0);
+    });
+
+    it('should validate with strict profile', async () => {
+      const workflow = {
+        ...SIMPLE_WEBHOOK_WORKFLOW,
+        name: createTestWorkflowName('Validate - Valid Strict'),
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      const response = await handleValidateWorkflow(
+        {
+          id: created.id,
+          options: { profile: 'strict' }
+        },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+      expect(data.valid).toBe(true);
+    });
+
+    it('should validate with ai-friendly profile', async () => {
+      const workflow = {
+        ...SIMPLE_WEBHOOK_WORKFLOW,
+        name: createTestWorkflowName('Validate - Valid AI Friendly'),
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      const response = await handleValidateWorkflow(
+        {
+          id: created.id,
+          options: { profile: 'ai-friendly' }
+        },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+      expect(data.valid).toBe(true);
+    });
+
+    it('should validate with minimal profile', async () => {
+      const workflow = {
+        ...SIMPLE_WEBHOOK_WORKFLOW,
+        name: createTestWorkflowName('Validate - Valid Minimal'),
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      const response = await handleValidateWorkflow(
+        {
+          id: created.id,
+          options: { profile: 'minimal' }
+        },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+      expect(data.valid).toBe(true);
+    });
+  });
+
+  // ======================================================================
+  // Invalid Workflow - Error Detection
+  // ======================================================================
+
+  describe('Invalid Workflow Detection', () => {
+    it('should detect invalid node type', async () => {
+      // Create workflow with invalid node type
+      const workflow = {
+        name: createTestWorkflowName('Validate - Invalid Node Type'),
+        nodes: [
+          {
+            id: 'invalid-1',
+            name: 'Invalid Node',
+            type: 'invalid-node-type',
+            typeVersion: 1,
+            position: [250, 300] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {},
+        settings: {},
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      const response = await handleValidateWorkflow(
+        { id: created.id },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+
+      // Should detect error
+      expect(data.valid).toBe(false);
+      expect(data.errors).toBeDefined();
+      expect(data.errors.length).toBeGreaterThan(0);
+      expect(data.summary.errorCount).toBeGreaterThan(0);
+
+      // Error should mention invalid node type
+      const errorMessages = data.errors.map((e: any) => e.message).join(' ');
+      expect(errorMessages).toMatch(/invalid-node-type|not found|unknown/i);
+    });
+
+    it('should detect missing required connections', async () => {
+      // Create workflow with 2 nodes but no connections
+      const workflow = {
+        name: createTestWorkflowName('Validate - Missing Connections'),
+        nodes: [
+          {
+            id: 'webhook-1',
+            name: 'Webhook',
+            type: 'n8n-nodes-base.webhook',
+            typeVersion: 2,
+            position: [250, 300] as [number, number],
+            parameters: {
+              httpMethod: 'GET',
+              path: 'test'
+            }
+          },
+          {
+            id: 'set-1',
+            name: 'Set',
+            type: 'n8n-nodes-base.set',
+            typeVersion: 3.4,
+            position: [450, 300] as [number, number],
+            parameters: {
+              assignments: {
+                assignments: []
+              }
+            }
+          }
+        ],
+        connections: {}, // Empty connections - Set node is unreachable
+        settings: {},
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      const response = await handleValidateWorkflow(
+        { id: created.id },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+
+      // Multi-node workflow with empty connections should produce warning/error
+      // (depending on validation profile)
+      expect(data.valid).toBe(false);
+    });
+  });
+
+  // ======================================================================
+  // Selective Validation
+  // ======================================================================
+
+  describe('Selective Validation', () => {
+    it('should validate nodes only (skip connections)', async () => {
+      const workflow = {
+        ...SIMPLE_WEBHOOK_WORKFLOW,
+        name: createTestWorkflowName('Validate - Nodes Only'),
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      const response = await handleValidateWorkflow(
+        {
+          id: created.id,
+          options: {
+            validateNodes: true,
+            validateConnections: false,
+            validateExpressions: false
+          }
+        },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+      expect(data.valid).toBe(true);
+    });
+
+    it('should validate connections only (skip nodes)', async () => {
+      const workflow = {
+        ...SIMPLE_WEBHOOK_WORKFLOW,
+        name: createTestWorkflowName('Validate - Connections Only'),
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      const response = await handleValidateWorkflow(
+        {
+          id: created.id,
+          options: {
+            validateNodes: false,
+            validateConnections: true,
+            validateExpressions: false
+          }
+        },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+      expect(data.valid).toBe(true);
+    });
+
+    it('should validate expressions only', async () => {
+      const workflow = {
+        ...SIMPLE_WEBHOOK_WORKFLOW,
+        name: createTestWorkflowName('Validate - Expressions Only'),
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      const response = await handleValidateWorkflow(
+        {
+          id: created.id,
+          options: {
+            validateNodes: false,
+            validateConnections: false,
+            validateExpressions: true
+          }
+        },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      // Expression validation may pass even if workflow has other issues
+      expect(response.data).toBeDefined();
+    });
+  });
+
+  // ======================================================================
+  // Error Handling
+  // ======================================================================
+
+  describe('Error Handling', () => {
+    it('should handle non-existent workflow ID', async () => {
+      const response = await handleValidateWorkflow(
+        { id: '99999999' },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(false);
+      expect(response.error).toBeDefined();
+    });
+
+    it('should handle invalid profile parameter', async () => {
+      const workflow = {
+        ...SIMPLE_WEBHOOK_WORKFLOW,
+        name: createTestWorkflowName('Validate - Invalid Profile'),
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      const response = await handleValidateWorkflow(
+        {
+          id: created.id,
+          options: { profile: 'invalid-profile' as any }
+        },
+        repository,
+        mcpContext
+      );
+
+      // Should either fail validation or use default profile
+      expect(response.success).toBe(false);
+    });
+  });
+
+  // ======================================================================
+  // Response Format Verification
+  // ======================================================================
+
+  describe('Response Format', () => {
+    it('should return complete validation response structure', async () => {
+      const workflow = {
+        ...SIMPLE_WEBHOOK_WORKFLOW,
+        name: createTestWorkflowName('Validate - Response Format'),
+        tags: ['mcp-integration-test']
+      };
+
+      const created = await client.createWorkflow(workflow);
+      context.trackWorkflow(created.id!);
+
+      const response = await handleValidateWorkflow(
+        { id: created.id },
+        repository,
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+
+      // Verify required fields
+      expect(data).toHaveProperty('workflowId');
+      expect(data).toHaveProperty('workflowName');
+      expect(data).toHaveProperty('valid');
+      expect(data).toHaveProperty('summary');
+
+      // errors and warnings only present if they exist
+      // For valid workflow, they should be undefined
+      if (data.errors) {
+        expect(Array.isArray(data.errors)).toBe(true);
+      }
+      if (data.warnings) {
+        expect(Array.isArray(data.warnings)).toBe(true);
+      }
+
+      // Verify summary structure
+      expect(data.summary).toHaveProperty('errorCount');
+      expect(data.summary).toHaveProperty('warningCount');
+      expect(data.summary).toHaveProperty('totalNodes');
+      expect(data.summary).toHaveProperty('enabledNodes');
+      expect(data.summary).toHaveProperty('triggerNodes');
+
+      // Verify types
+      expect(typeof data.valid).toBe('boolean');
+      expect(typeof data.summary.errorCount).toBe('number');
+      expect(typeof data.summary.warningCount).toBe('number');
+    });
+  });
+});