diff --git a/lib/platform/bitbucket/__snapshots__/index.spec.ts.snap b/lib/platform/bitbucket/__snapshots__/index.spec.ts.snap
index dfd3a2f8d645c2..76786c3e693e82 100644
--- a/lib/platform/bitbucket/__snapshots__/index.spec.ts.snap
+++ b/lib/platform/bitbucket/__snapshots__/index.spec.ts.snap
@@ -1344,12 +1344,23 @@ Array [
     "url": "https://api.bitbucket.org/2.0/repositories/some/repo",
   },
   Object {
-    "body": "{\\"title\\":\\"title\\",\\"description\\":\\"body\\"}",
     "headers": Object {
       "accept": "application/json",
       "accept-encoding": "gzip, deflate",
       "authorization": "Basic YWJjOjEyMw==",
-      "content-length": 38,
+      "host": "api.bitbucket.org",
+      "user-agent": "https://github.com/renovatebot/renovate",
+    },
+    "method": "GET",
+    "url": "https://api.bitbucket.org/2.0/repositories/some/repo/pullrequests/5",
+  },
+  Object {
+    "body": "{\\"title\\":\\"title\\",\\"description\\":\\"body\\",\\"reviewers\\":[{\\"display_name\\":\\"Jane Smith\\",\\"uuid\\":\\"{90b6646d-1724-4a64-9fd9-539515fe94e9}\\"}]}",
+    "headers": Object {
+      "accept": "application/json",
+      "accept-encoding": "gzip, deflate",
+      "authorization": "Basic YWJjOjEyMw==",
+      "content-length": 130,
       "content-type": "application/json",
       "host": "api.bitbucket.org",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -1359,3 +1370,32 @@ Array [
   },
 ]
 `;
+
+exports[`platform/bitbucket updatePr() throws an error on failure to get current list of reviewers 1`] = `"Response code 500 (Internal Server Error)"`;
+
+exports[`platform/bitbucket updatePr() throws an error on failure to get current list of reviewers 2`] = `
+Array [
+  Object {
+    "headers": Object {
+      "accept": "application/json",
+      "accept-encoding": "gzip, deflate",
+      "authorization": "Basic YWJjOjEyMw==",
+      "host": "api.bitbucket.org",
+      "user-agent": "https://github.com/renovatebot/renovate",
+    },
+    "method": "GET",
+    "url": "https://api.bitbucket.org/2.0/repositories/some/repo",
+  },
+  Object {
+    "headers": Object {
+      "accept": "application/json",
+      "accept-encoding": "gzip, deflate",
+      "authorization": "Basic YWJjOjEyMw==",
+      "host": "api.bitbucket.org",
+      "user-agent": "https://github.com/renovatebot/renovate",
+    },
+    "method": "GET",
+    "url": "https://api.bitbucket.org/2.0/repositories/some/repo/pullrequests/5",
+  },
+]
+`;
diff --git a/lib/platform/bitbucket/index.spec.ts b/lib/platform/bitbucket/index.spec.ts
index e748bea7dee5de..9ae1831a45ba25 100644
--- a/lib/platform/bitbucket/index.spec.ts
+++ b/lib/platform/bitbucket/index.spec.ts
@@ -773,11 +773,29 @@ describe('platform/bitbucket', () => {
 
   describe('updatePr()', () => {
     it('puts PR', async () => {
+      const reviewer = {
+        display_name: 'Jane Smith',
+        uuid: '{90b6646d-1724-4a64-9fd9-539515fe94e9}',
+      };
       const scope = await initRepoMock();
-      scope.put('/2.0/repositories/some/repo/pullrequests/5').reply(200);
+      scope
+        .get('/2.0/repositories/some/repo/pullrequests/5')
+        .reply(200, { reviewers: [reviewer] })
+        .put('/2.0/repositories/some/repo/pullrequests/5')
+        .reply(200);
       await bitbucket.updatePr(5, 'title', 'body');
       expect(httpMock.getTrace()).toMatchSnapshot();
     });
+    it('throws an error on failure to get current list of reviewers', async () => {
+      const scope = await initRepoMock();
+      scope
+        .get('/2.0/repositories/some/repo/pullrequests/5')
+        .reply(500, undefined);
+      await expect(() =>
+        bitbucket.updatePr(5, 'title', 'body')
+      ).rejects.toThrowErrorMatchingSnapshot();
+      expect(httpMock.getTrace()).toMatchSnapshot();
+    });
   });
 
   describe('mergePr()', () => {
diff --git a/lib/platform/bitbucket/index.ts b/lib/platform/bitbucket/index.ts
index f3e217b521f542..19089d509d2d12 100644
--- a/lib/platform/bitbucket/index.ts
+++ b/lib/platform/bitbucket/index.ts
@@ -281,6 +281,7 @@ interface PrResponse {
       name: string;
     };
   };
+  reviewers: Array<any>;
 }
 
 // Gets details for a PR
@@ -785,10 +786,21 @@ export async function updatePr(
   description: string
 ): Promise<void> {
   logger.debug(`updatePr(${prNo}, ${title}, body)`);
+  // Updating a PR in Bitbucket will clear the reviewers if reviewers is not present
+  const pr = (
+    await bitbucketHttp.getJson<PrResponse>(
+      `/2.0/repositories/${config.repository}/pullrequests/${prNo}`
+    )
+  ).body;
+
   await bitbucketHttp.putJson(
     `/2.0/repositories/${config.repository}/pullrequests/${prNo}`,
     {
-      body: { title, description: sanitize(description) },
+      body: {
+        title,
+        description: sanitize(description),
+        reviewers: pr.reviewers,
+      },
     }
   );
 }