diff --git a/services/bots/src/github-webhook/github-webhook.const.ts b/services/bots/src/github-webhook/github-webhook.const.ts
index b27218d..92f9ac8 100644
--- a/services/bots/src/github-webhook/github-webhook.const.ts
+++ b/services/bots/src/github-webhook/github-webhook.const.ts
@@ -15,6 +15,8 @@ export type GetIssueResponse = RestEndpointMethodTypes['issues']['get']['respons
 export type GetIssueLabelParams = RestEndpointMethodTypes['issues']['getLabel']['parameters'];
 export type GetIssueLabelResponse =
   RestEndpointMethodTypes['issues']['getLabel']['response']['data'];
+export type PullRequestCreateReviewParams =
+  RestEndpointMethodTypes['pulls']['createReview']['parameters'];
 
 export type Repository = HomeAssistantRepository;
 
diff --git a/services/bots/src/github-webhook/github-webhook.module.ts b/services/bots/src/github-webhook/github-webhook.module.ts
index 5a0825f..25eff4b 100644
--- a/services/bots/src/github-webhook/github-webhook.module.ts
+++ b/services/bots/src/github-webhook/github-webhook.module.ts
@@ -17,6 +17,7 @@ import { IssueCommentCommands } from './handlers/issue_comment_commands/handler'
 import { IssueLinks } from './handlers/issue_links';
 import { LabelBot } from './handlers/label_bot/handler';
 import { LabelCleaner } from './handlers/label_cleaner';
+import { MergeConflictChecker } from './handlers/merge_conflict';
 import { MonthOfWTH } from './handlers/month_of_wth';
 import { NewIntegrationsHandler } from './handlers/new_integrations';
 import { PlatinumReview } from './handlers/platinum_review';
@@ -40,6 +41,7 @@ import { ValidateCla } from './handlers/validate-cla';
     IssueLinks,
     LabelBot,
     LabelCleaner,
+    MergeConflictChecker,
     MonthOfWTH,
     NewIntegrationsHandler,
     PlatinumReview,
diff --git a/services/bots/src/github-webhook/handlers/merge_conflict.ts b/services/bots/src/github-webhook/handlers/merge_conflict.ts
new file mode 100644
index 0000000..0becfa2
--- /dev/null
+++ b/services/bots/src/github-webhook/handlers/merge_conflict.ts
@@ -0,0 +1,27 @@
+import { PullRequestOpenedEvent, PullRequestSynchronizeEvent } from '@octokit/webhooks-types';
+import { EventType, HomeAssistantRepository } from '../github-webhook.const';
+import { WebhookContext } from '../github-webhook.model';
+import { BaseWebhookHandler } from './base';
+
+export class MergeConflictChecker extends BaseWebhookHandler {
+  public allowedEventTypes = [EventType.PULL_REQUEST_OPENED, EventType.PULL_REQUEST_SYNCHRONIZE];
+  public allowedRepositories = [HomeAssistantRepository.CORE];
+
+  async handle(context: WebhookContext<PullRequestOpenedEvent | PullRequestSynchronizeEvent>) {
+    // The data in the event is stale, so we need to re-fetch it.
+    const { data: pullRequest } = await context.github.pulls.get(context.pullRequest());
+
+    if (pullRequest.mergeable_state !== 'dirty') {
+      // The Pull request is not dirty.
+      return;
+    }
+
+    // Create a review with a comment to let the user know that there is a merge conflict.
+    await context.github.pulls.createReview(
+      context.pullRequest({
+        body: `There is a merge conflict.`,
+        event: 'REQUEST_CHANGES',
+      }),
+    );
+  }
+}
diff --git a/tests/services/bots/github-webhook/handlers/merge_conflict.spec.ts b/tests/services/bots/github-webhook/handlers/merge_conflict.spec.ts
new file mode 100644
index 0000000..d6305c2
--- /dev/null
+++ b/tests/services/bots/github-webhook/handlers/merge_conflict.spec.ts
@@ -0,0 +1,57 @@
+// @ts-nocheck
+import * as assert from 'assert';
+import { WebhookContext } from '../../../../../bots/src/github-webhook/github-webhook.model';
+import { MergeConflictChecker } from '../../../../../services/bots/src/github-webhook/handlers/merge_conflict';
+import { mockWebhookContext } from '../../../../utils/test_context';
+import { loadJsonFixture } from '../../../../utils/fixture';
+
+describe('MergeConflictChecker', () => {
+  let handler: MergeConflictChecker;
+  let mockContext: WebhookContext<any>;
+  let getPullResponse: any;
+  let createReviewContents: PullRequestCreateReviewParams;
+
+  beforeEach(function () {
+    handler = new MergeConflictChecker();
+    getPullResponse = { data: {} };
+    createReviewContents = {};
+    mockContext = mockWebhookContext({
+      eventType: 'pull_request.opened',
+      payload: loadJsonFixture('pull_request.opened', {}),
+      github: {
+        pulls: {
+          async get() {
+            return getPullResponse;
+          },
+          async createReview(params: PullRequestCreateReviewParams) {
+            createReviewContents = params;
+          },
+        },
+      },
+    });
+  });
+
+  it('PR with clean state', async () => {
+    mockContext.github.pulls.createReview = jest.fn();
+    getPullResponse = { data: { mergeable_state: 'clean' } };
+
+    await handler.handle(mockContext);
+
+    assert.deepStrictEqual(createReviewContents, {});
+    expect(mockContext.github.pulls.createReview).not.toHaveBeenCalled();
+  });
+
+  it('PR with dirty state', async () => {
+    getPullResponse = { data: { mergeable_state: 'dirty' } };
+
+    await handler.handle(mockContext);
+
+    assert.deepStrictEqual(createReviewContents, {
+      body: 'There is a merge conflict.',
+      event: 'REQUEST_CHANGES',
+      owner: 'Codertocat',
+      pull_number: 2,
+      repo: 'Hello-World',
+    });
+  });
+});