diff --git a/src/azure.ts b/src/azure.ts
index 5719fc40c..97765df6d 100644
--- a/src/azure.ts
+++ b/src/azure.ts
@@ -1,4 +1,6 @@
 import type { RequestInit } from './internal/builtin-types';
+import type { NullableHeaders } from './internal/headers';
+import { buildHeaders } from './internal/headers';
 import * as Errors from './error';
 import { FinalRequestOptions } from './internal/request-options';
 import { isObj, readEnv } from './internal/utils';
@@ -134,6 +136,13 @@ export class AzureOpenAI extends OpenAI {
     }
     return super.buildRequest(options, props);
   }
+
+  protected override async authHeaders(opts: FinalRequestOptions): Promise<NullableHeaders | undefined> {
+    if (typeof this._options.apiKey === 'string') {
+      return buildHeaders([{ 'api-key': this.apiKey }]);
+    }
+    return super.authHeaders(opts);
+  }
 }
 
 const _deployments_endpoints = new Set([
diff --git a/src/client.ts b/src/client.ts
index cc2cc0a30..b3c899b44 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -331,7 +331,7 @@ export class OpenAI {
   private fetch: Fetch;
   #encoder: Opts.RequestEncoder;
   protected idempotencyHeader?: string;
-  private _options: ClientOptions;
+  protected _options: ClientOptions;
 
   /**
    * API Client for interfacing with the OpenAI API.
diff --git a/tests/lib/azure.test.ts b/tests/lib/azure.test.ts
index b93defab0..82af3ec85 100644
--- a/tests/lib/azure.test.ts
+++ b/tests/lib/azure.test.ts
@@ -307,6 +307,22 @@ describe('instantiate azure client', () => {
     });
   });
 
+  test('uses api-key header when apiKey is provided', async () => {
+    const testFetch = async (url: RequestInfo, { headers }: RequestInit = {}): Promise<Response> => {
+      return new Response(JSON.stringify({ a: 1 }), { headers: headers ?? [] });
+    };
+    const client = new AzureOpenAI({
+      baseURL: 'http://localhost:5000/',
+      apiKey: 'My API Key',
+      apiVersion,
+      fetch: testFetch,
+    });
+
+    const res = await client.request({ method: 'post', path: 'https://example.com' }).asResponse();
+    expect(res.headers.get('api-key')).toEqual('My API Key');
+    expect(res.headers.get('authorization')).toEqual(null);
+  });
+
   test('with endpoint', () => {
     const client = new AzureOpenAI({ endpoint: 'https://example.com', apiKey: 'My API Key', apiVersion });
     expect(client.baseURL).toEqual('https://example.com/openai');