diff --git a/src/index.ts b/src/index.ts
index 9edb6e6..3e1bc51 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -128,6 +128,11 @@ const tools: Tool[] = [
           },
           description: 'Array of component names',
         },
+        customFields: {
+          type: 'object',
+          description: 'Map of additional Jira field IDs/keys (e.g., customfield_10211) to include in the fields payload',
+          additionalProperties: true,
+        },
       },
       required: ['projectKey', 'summary', 'issueType'],
     },
@@ -169,6 +174,11 @@ const tools: Tool[] = [
           type: 'string',
           description: 'New status/workflow state (e.g., "In Progress", "Done")',
         },
+        customFields: {
+          type: 'object',
+          description: 'Map of additional Jira field IDs/keys (e.g., customfield_10211) to include in the fields payload',
+          additionalProperties: true,
+        },
       },
       required: ['issueKey'],
     },
@@ -346,6 +356,7 @@ server.setRequestHandler(CallToolRequestSchema, async (request) => {
           assignee: args.assignee as string,
           labels: args.labels as string[],
           components: args.components as string[],
+          customFields: args.customFields as Record<string, any>,
         };
         const issue = await getJiraClient().createIssue(input);
         return {
@@ -365,6 +376,7 @@ server.setRequestHandler(CallToolRequestSchema, async (request) => {
           assignee: args.assignee as string,
           priority: args.priority as string,
           labels: args.labels as string[],
+          customFields: args.customFields as Record<string, any>,
           status: args.status as string,
         };
         const issue = await getJiraClient().updateIssue(args.issueKey as string, input);
diff --git a/src/jira-client.ts b/src/jira-client.ts
index 6fc0a47..3a71d0f 100644
--- a/src/jira-client.ts
+++ b/src/jira-client.ts
@@ -52,6 +52,8 @@ export interface CreateIssueInput {
   assignee?: string;
   labels?: string[];
   components?: string[];
+  // Pass-through map for Jira custom fields (e.g., { customfield_10211: 10015 })
+  customFields?: Record<string, any>;
 }
 
 export interface UpdateIssueInput {
@@ -61,6 +63,8 @@ export interface UpdateIssueInput {
   priority?: string;
   labels?: string[];
   status?: string;
+  // Pass-through map for Jira custom fields to update
+  customFields?: Record<string, any>;
 }
 
 export interface JiraComment {
@@ -138,6 +142,11 @@ export class JiraClient {
       issueData.fields.components = input.components.map(c => ({ name: c }));
     }
 
+    // Merge any provided custom fields directly into the fields payload
+    if (input.customFields && typeof input.customFields === 'object') {
+      Object.assign(issueData.fields, input.customFields);
+    }
+
     const response = await this.client.post('/issue', issueData);
     return await this.getIssue(response.data.key);
   }
@@ -167,6 +176,11 @@ export class JiraClient {
       updateData.fields.labels = input.labels;
     }
 
+    // Merge any provided custom fields directly into the fields payload
+    if (input.customFields && typeof input.customFields === 'object') {
+      Object.assign(updateData.fields, input.customFields);
+    }
+
     await this.client.put(`/issue/${issueKey}`, updateData);
 
     // Handle status transition separately if provided