diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6c16093..ee758d5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,20 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.9.1] - 2025-01-27
+
+### Fixed
+- **Fixed `update_pull_request` reviewer preservation**:
+  - When updating a PR without specifying reviewers, existing reviewers are now preserved
+  - Previously, omitting the `reviewers` parameter would clear all reviewers
+  - Now properly includes existing reviewers in the API request when not explicitly updating them
+  - When updating reviewers, approval status is preserved for existing reviewers
+  - This prevents accidentally removing reviewers when only updating PR title or description
+
+### Changed
+- Updated tool documentation to clarify reviewer behavior in `update_pull_request`
+- Enhanced README with detailed explanation of reviewer handling
+
 ## [0.9.0] - 2025-01-26
 
 ### Added
diff --git a/README.md b/README.md
index 1f1cfcb..0e4ab2d 100644
--- a/README.md
+++ b/README.md
@@ -264,11 +264,19 @@ Returns a paginated list of pull requests with:
     "title": "Updated title",  // Optional
     "description": "Updated description",  // Optional
     "destination_branch": "develop",  // Optional
-    "reviewers": ["new.reviewer"]  // Optional - replaces existing reviewers
+    "reviewers": ["new.reviewer"]  // Optional - see note below
   }
 }
 ```
 
+**Important Note on Reviewers:**
+- When updating a PR without specifying the `reviewers` parameter, existing reviewers and their approval status are preserved
+- When providing the `reviewers` parameter:
+  - The reviewer list is replaced with the new list
+  - For reviewers that already exist on the PR, their approval status is preserved
+  - New reviewers are added without approval status
+- This prevents accidentally removing reviewers when you only want to update the PR description or title
+
 ### Add Comment
 
 Add a comment to a pull request, either as a general comment or inline on specific code:
diff --git a/package.json b/package.json
index 3627092..627fb14 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@nexus2520/bitbucket-mcp-server",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "description": "MCP server for Bitbucket API integration - supports both Cloud and Server",
   "type": "module",
   "main": "./build/index.js",
diff --git a/src/handlers/pull-request-handlers.ts b/src/handlers/pull-request-handlers.ts
index 7ec337c..ba761f5 100644
--- a/src/handlers/pull-request-handlers.ts
+++ b/src/handlers/pull-request-handlers.ts
@@ -348,7 +348,7 @@ export class PullRequestHandlers {
         // Bitbucket Server API
         apiPath = `/rest/api/1.0/projects/${workspace}/repos/${repository}/pull-requests/${pull_request_id}`;
         
-        // First get the current PR to get version number
+        // First get the current PR to get version number and existing data
         const currentPr = await this.apiClient.makeRequest<any>('get', apiPath);
         
         requestBody.version = currentPr.version;
@@ -365,8 +365,28 @@ export class PullRequestHandlers {
             }
           };
         }
+        
+        // Handle reviewers: preserve existing ones if not explicitly updating
         if (reviewers !== undefined) {
-          requestBody.reviewers = reviewers.map(r => ({ user: { name: r } }));
+          // User wants to update reviewers
+          // Create a map of existing reviewers for preservation of approval status
+          const existingReviewersMap = new Map(
+            currentPr.reviewers.map((r: any) => [r.user.name, r])
+          );
+          
+          requestBody.reviewers = reviewers.map(username => {
+            const existing = existingReviewersMap.get(username);
+            if (existing) {
+              // Preserve existing reviewer's full data including approval status
+              return existing;
+            } else {
+              // Add new reviewer (without approval status)
+              return { user: { name: username } };
+            }
+          });
+        } else {
+          // No reviewers provided - preserve existing reviewers with their full data
+          requestBody.reviewers = currentPr.reviewers;
         }
       } else {
         // Bitbucket Cloud API
diff --git a/src/index.ts b/src/index.ts
index ddc6131..bc773a0 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -40,7 +40,7 @@ class BitbucketMCPServer {
     this.server = new Server(
       {
         name: 'bitbucket-mcp-server',
-        version: '0.9.0',
+        version: '0.9.1',
       },
       {
         capabilities: {
diff --git a/src/tools/definitions.ts b/src/tools/definitions.ts
index 5d0ff44..0f25f51 100644
--- a/src/tools/definitions.ts
+++ b/src/tools/definitions.ts
@@ -101,7 +101,7 @@ export const toolDefinitions = [
   },
   {
     name: 'update_pull_request',
-    description: 'Update an existing pull request',
+    description: 'Update an existing pull request. When updating without specifying reviewers, existing reviewers and their approval status will be preserved.',
     inputSchema: {
       type: 'object',
       properties: {
@@ -132,7 +132,7 @@ export const toolDefinitions = [
         reviewers: {
           type: 'array',
           items: { type: 'string' },
-          description: 'New list of reviewer usernames/emails (optional)',
+          description: 'New list of reviewer usernames/emails. If provided, replaces the reviewer list (preserving approval status for existing reviewers). If omitted, existing reviewers are preserved. (optional)',
         },
       },
       required: ['workspace', 'repository', 'pull_request_id'],