diff --git a/src/lib/responses/ResponseStream.ts b/src/lib/responses/ResponseStream.ts
index 652c81ceda..bfef366e64 100644
--- a/src/lib/responses/ResponseStream.ts
+++ b/src/lib/responses/ResponseStream.ts
@@ -10,7 +10,11 @@ import { RequestOptions } from '../../internal/request-options';
 import { APIUserAbortError, OpenAIError } from '../../error';
 import OpenAI from '../../index';
 import { type BaseEvents, EventStream } from '../EventStream';
-import { type ResponseFunctionCallArgumentsDeltaEvent, type ResponseTextDeltaEvent } from './EventTypes';
+import {
+  type ResponseFunctionCallArgumentsDeltaEvent,
+  type ResponseRefusalDeltaEvent,
+  type ResponseTextDeltaEvent,
+} from './EventTypes';
 import { maybeParseResponse, ParseableToolsParams } from '../ResponsesParser';
 import { Stream } from '../../streaming';
 
@@ -278,6 +282,23 @@ export class ResponseStream<ParsedT = null>
         }
         break;
       }
+      case 'response.refusal.delta': {
+        const output = snapshot.output[event.output_index];
+        if (!output) {
+          throw new OpenAIError(`missing output at index ${event.output_index}`);
+        }
+        if (output.type === 'message') {
+          const content = output.content[event.content_index];
+          if (!content) {
+            throw new OpenAIError(`missing content at index ${event.content_index}`);
+          }
+          if (content.type !== 'refusal') {
+            throw new OpenAIError(`expected content to be 'refusal', got ${content.type}`);
+          }
+          content.refusal += event.delta;
+        }
+        break;
+      }
       case 'response.completed': {
         this.#currentResponseSnapshot = event.response;
         break;
diff --git a/tests/lib/ResponseStream.test.ts b/tests/lib/ResponseStream.test.ts
index 9797baa6d0..3b541d5a0b 100644
--- a/tests/lib/ResponseStream.test.ts
+++ b/tests/lib/ResponseStream.test.ts
@@ -31,6 +31,31 @@ describe('.stream()', () => {
     }
   });
 
+  it('refusal accumulates correctly', async () => {
+    const deltas: string[] = [];
+
+    const stream = (
+      await makeStreamSnapshotRequest((openai) =>
+        openai.responses.stream({
+          model: 'gpt-4o-2024-08-06',
+          input: 'Do something harmful',
+        }),
+      )
+    ).on('response.refusal.delta', (e) => {
+      deltas.push(e.delta);
+    });
+
+    const final = await stream.finalResponse();
+    // The three deltas must be concatenated into the snapshot's refusal content
+    expect(deltas).toEqual(['I cannot ', 'help with ', 'that.']);
+
+    const msg = final.output[0];
+    expect(msg?.type).toBe('message');
+    if (msg?.type === 'message') {
+      expect(msg.content[0]).toMatchObject({ type: 'refusal', refusal: 'I cannot help with that.' });
+    }
+  });
+
   it('reasoning works', async () => {
     const stream = await makeStreamSnapshotRequest((openai) =>
       openai.responses.stream({
diff --git a/tests/lib/__snapshots__/ResponseStream.test.ts.snap b/tests/lib/__snapshots__/ResponseStream.test.ts.snap
index 2ebb08c676..3a81f1c1c5 100644
--- a/tests/lib/__snapshots__/ResponseStream.test.ts.snap
+++ b/tests/lib/__snapshots__/ResponseStream.test.ts.snap
@@ -22,6 +22,30 @@ data: [DONE]
 "
 `;
 
+exports[`.stream() refusal accumulates correctly 1`] = `
+"data: {\"response\":{\"id\":\"resp_refusal_1\",\"object\":\"response\",\"created_at\":1723031665,\"model\":\"gpt-4o-2024-08-06\",\"output\":[],\"output_text\":\"\",\"error\":null,\"incomplete_details\":null,\"instructions\":null,\"metadata\":null,\"parallel_tool_calls\":false,\"temperature\":null,\"tools\":[],\"top_p\":null,\"status\":\"in_progress\",\"usage\":{\"input_tokens\":0,\"input_tokens_details\":{\"cached_tokens\":0},\"output_tokens\":0,\"output_tokens_details\":{\"reasoning_tokens\":0},\"total_tokens\":0}},\"sequence_number\":0,\"type\":\"response.created\"}
+
+data: {\"item\":{\"id\":\"msg_ref_1\",\"type\":\"message\",\"role\":\"assistant\",\"status\":\"in_progress\",\"content\":[]},\"output_index\":0,\"sequence_number\":1,\"type\":\"response.output_item.added\"}
+
+data: {\"content_index\":0,\"item_id\":\"msg_ref_1\",\"output_index\":0,\"part\":{\"type\":\"refusal\",\"refusal\":\"\"},\"sequence_number\":2,\"type\":\"response.content_part.added\"}
+
+data: {\"content_index\":0,\"delta\":\"I cannot \",\"item_id\":\"msg_ref_1\",\"output_index\":0,\"sequence_number\":3,\"type\":\"response.refusal.delta\"}
+
+data: {\"content_index\":0,\"delta\":\"help with \",\"item_id\":\"msg_ref_1\",\"output_index\":0,\"sequence_number\":4,\"type\":\"response.refusal.delta\"}
+
+data: {\"content_index\":0,\"delta\":\"that.\",\"item_id\":\"msg_ref_1\",\"output_index\":0,\"sequence_number\":5,\"type\":\"response.refusal.delta\"}
+
+data: {\"content_index\":0,\"item_id\":\"msg_ref_1\",\"output_index\":0,\"refusal\":\"I cannot help with that.\",\"sequence_number\":6,\"type\":\"response.refusal.done\"}
+
+data: {\"item\":{\"id\":\"msg_ref_1\",\"type\":\"message\",\"role\":\"assistant\",\"status\":\"completed\",\"content\":[{\"type\":\"refusal\",\"refusal\":\"I cannot help with that.\"}]},\"output_index\":0,\"sequence_number\":7,\"type\":\"response.output_item.done\"}
+
+data: {\"response\":{\"id\":\"resp_refusal_1\",\"object\":\"response\",\"created_at\":1723031665,\"model\":\"gpt-4o-2024-08-06\",\"output\":[{\"id\":\"msg_ref_1\",\"type\":\"message\",\"role\":\"assistant\",\"status\":\"completed\",\"content\":[{\"type\":\"refusal\",\"refusal\":\"I cannot help with that.\"}]}],\"output_text\":\"\",\"error\":null,\"incomplete_details\":null,\"instructions\":null,\"metadata\":null,\"parallel_tool_calls\":false,\"temperature\":null,\"tools\":[],\"top_p\":null,\"status\":\"completed\",\"usage\":{\"input_tokens\":10,\"input_tokens_details\":{\"cached_tokens\":0},\"output_tokens\":5,\"output_tokens_details\":{\"reasoning_tokens\":0},\"total_tokens\":15}},\"sequence_number\":8,\"type\":\"response.completed\"}
+
+data: [DONE]
+
+"
+`;
+
 exports[`.stream() reasoning works 1`] = `
 "data: {\"response\":{\"id\":\"resp_reason_1\",\"object\":\"response\",\"created_at\":1723031666,\"model\":\"o3\",\"output\":[],\"output_text\":\"\",\"error\":null,\"incomplete_details\":null,\"instructions\":null,\"metadata\":null,\"parallel_tool_calls\":false,\"temperature\":null,\"tools\":[],\"top_p\":null,\"status\":\"in_progress\",\"usage\":{\"input_tokens\":0,\"input_tokens_details\":{\"cached_tokens\":0},\"output_tokens\":0,\"output_tokens_details\":{\"reasoning_tokens\":0},\"total_tokens\":0}},\"sequence_number\":0,\"type\":\"response.created\"}