diff --git a/src/features/chat/api/room.ts b/src/features/chat/api/room.ts
index 21dbfd4..ef1cf3e 100644
--- a/src/features/chat/api/room.ts
+++ b/src/features/chat/api/room.ts
@@ -4,12 +4,12 @@ import type { ChatProduct, ChatRole, SaleStatus, TradeStatus } from '../model/ty
 import type { ChatRoomDetailResponse, ProductStatus } from './dto';
 
 // 채팅방 생성 또는 조회 (아이템 상세 페이지 채팅하기 버튼).
-// 판매자가 받은 구매 제안 상세에서 열 땐 purchaseOfferId를 함께 보내 제안자↔소유자 방을 잡는다.
 export const createOrGetChatRoom = (itemId: number, purchaseOfferId?: number) =>
-  api.post<{ chatRoomId: number }>('/chats', {
-    itemId,
-    ...(purchaseOfferId != null && { purchaseOfferId }),
-  });
+  api.post<{ chatRoomId: number }>('/chats', { itemId, purchaseOfferId });
+
+// 채팅방 생성 또는 조회 (거래 상세 페이지 채팅하기 버튼).
+export const createOrGetChatRoomByTrade = (tradeId: number) =>
+  api.post<{ chatRoomId: number }>(`/chats/trades/${tradeId}`);
 
 // 채팅방 상세 조회 (프로덕트 바 데이터)
 export const getChatRoom = (chatRoomId: number) => {
diff --git a/src/pages/mypage/TradeDetailPage.tsx b/src/pages/mypage/TradeDetailPage.tsx
index ba83116..44a761d 100644
--- a/src/pages/mypage/TradeDetailPage.tsx
+++ b/src/pages/mypage/TradeDetailPage.tsx
@@ -8,7 +8,7 @@ import { useTradeStatusChange } from '@/features/trade/api/useTradeStatusChange'
 import type { TradeStatus } from '@/features/trade/api/types';
 import { buildTradeTimeline } from '@/features/trade/lib/buildTradeTimeline';
 import { resolveImageUrl } from '@/shared/lib/resolveImageUrl';
-import { createOrGetChatRoom } from '@/features/chat/api/room';
+import { createOrGetChatRoomByTrade } from '@/features/chat/api/room';
 
 const SectionTitle = ({ children }: { children: ReactNode }) => (
   <p className="px-[16px] pt-[24px] pb-[8px] text-[12px] text-[#767676]">{children}</p>
@@ -152,7 +152,7 @@ const TradeDetailPage = () => {
     if (isChatLoading) return;
     setIsChatLoading(true);
     try {
-      const { chatRoomId } = await createOrGetChatRoom(trade.itemId);
+      const { chatRoomId } = await createOrGetChatRoomByTrade(trade.tradeId);
       navigate(`/chat/${chatRoomId}`);
     } finally {
       setIsChatLoading(false);