diff --git a/src/main/java/com/tenure/domain/chat/controller/ChatController.java b/src/main/java/com/tenure/domain/chat/controller/ChatController.java
index 3b8fcd52..418e7338 100644
--- a/src/main/java/com/tenure/domain/chat/controller/ChatController.java
+++ b/src/main/java/com/tenure/domain/chat/controller/ChatController.java
@@ -76,6 +76,17 @@ public BaseResponse<ChatRoomResponse> getChatRoom(@PathVariable Long chatRoomId)
         return BaseResponse.success(chatRoomResponse);
     }
 
+    @Operation(
+            summary = "거래 기반 채팅방 생성 또는 조회",
+            description = "거래 상세 화면에서 채팅하기 버튼 클릭 시 호출합니다. 구매자/판매자 모두 사용 가능합니다."
+    )
+    @PostMapping("/trades/{tradeId}")
+    public BaseResponse<ChatRoomResponse> findOrCreateChatRoomByTrade(@PathVariable Long tradeId) {
+        ChatRoomResponse chatRoomResponse = chatRoomService
+                .findOrCreateChatRoomByTrade(currentUserProvider.getCurrentUserId(), tradeId);
+        return BaseResponse.success(chatRoomResponse);
+    }
+
     @Operation(
             summary = "채팅방 읽음 처리",
             description = "채팅방 접속 시 호출합니다. 읽지 않은 메시지 수를 0으로 초기화합니다."
diff --git a/src/main/java/com/tenure/domain/chat/service/ChatRoomService.java b/src/main/java/com/tenure/domain/chat/service/ChatRoomService.java
index fa02a575..10e36f48 100644
--- a/src/main/java/com/tenure/domain/chat/service/ChatRoomService.java
+++ b/src/main/java/com/tenure/domain/chat/service/ChatRoomService.java
@@ -28,6 +28,7 @@
 import com.tenure.domain.purchase.repository.PurchaseIntentRepository;
 import com.tenure.domain.purchase.repository.PurchaseOfferRepository;
 import com.tenure.domain.trade.entity.Trade;
+import com.tenure.domain.trade.exception.TradeErrorCode;
 import com.tenure.domain.trade.repository.TradeRepository;
 import com.tenure.domain.user.entity.User;
 import com.tenure.domain.user.entity.UserBlock;
@@ -38,6 +39,7 @@
 import com.tenure.global.storage.ImageStorageService;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import org.jspecify.annotations.NonNull;
 import org.springframework.dao.DataIntegrityViolationException;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Slice;
@@ -176,21 +178,7 @@ public ChatRoomResponse findOrCreateChatRoom(Long currentUserId, Long itemId, Lo
                     return offerSentProduct;
                 });
 
-        ChatRoom  chatRoom;
-
-        // 사용자가 동시에 채팅방 생성을 할 경우 방지
-        try {
-            //체팅방을 조회(닫히지 않은 채팅방) / 없으면 새로 만든 후 저장
-            chatRoom = chatRoomRepository.findByItemIdAndSellerIdAndBuyerIdAndIsClosedFalse(itemId, owner.getId(), buyerId)
-                    .orElseGet(() -> createChatRoom(item, buyer, owner));
-        } catch (DataIntegrityViolationException e) {
-            chatRoom = chatRoomRepository.findByItemIdAndSellerIdAndBuyerIdAndIsClosedFalse(itemId, owner.getId(), buyerId)
-                    .orElseThrow(() -> {
-                        log.warn("[채팅방 생성/조회] 채팅방을 찾을 수 없습니다. itemId = {}, ownerId = {}, buyerId = {}", itemId, owner.getId(), buyerId );
-                        return new CustomException(ChatErrorCode.CHAT_ROOM_NOT_FOUND);
-                    });
-        }
-
+        ChatRoom  chatRoom = findOrCreateChatRoom(itemId, owner, buyerId, item, buyer);
 
 
         Long tradeId = tradeRepository.findByItemId(itemId).map(Trade::getId).orElse(null);
@@ -213,6 +201,85 @@ public ChatRoomResponse findOrCreateChatRoom(Long currentUserId, Long itemId, Lo
                 .from(chatRoom, item, product, currentUserId, tradeId, purchaseIntentId, sentPurchaseOfferId, ownerBlockedBuyer, false, offerPrice);
     }
 
+    // 거래 기반 채팅방 조회 / 생성 (TradeDetailPage)
+    @Transactional
+    public ChatRoomResponse findOrCreateChatRoomByTrade(Long currentUserId, Long tradeId) {
+
+        log.info("[거래 기반 채팅방 생성/조회] currentUserId = {}, tradeId = {}", currentUserId, tradeId);
+
+        Trade trade = tradeRepository.findByIdWithParticipants(tradeId)
+                .orElseThrow(() -> {
+                    log.warn("[거래 기반 채팅방 생성/조회] 거래를 찾을 수 없습니다. tradeId = {}", tradeId);
+                    return new CustomException(TradeErrorCode.TRADE_NOT_FOUND);
+                });
+
+        // 구매자, 판매자, 아이템 조회
+        User buyer = trade.getBuyer();
+        User owner = trade.getSeller();
+        Long buyerId = buyer.getId();
+        Item item = trade.getItem();
+        Long itemId = item.getId();
+
+        // 거래 참여자인지 검증
+        boolean isBuyer = currentUserId.equals(buyerId);
+        boolean isSeller = currentUserId.equals(owner.getId());
+        if (!isBuyer && !isSeller) {
+            log.warn("[거래 기반 채팅방 생성/조회] 거래 참여자가 아닙니다. currentUserId = {}", currentUserId);
+            throw new CustomException(ChatErrorCode.CHAT_CREATION_NOT_ALLOWED);
+        }
+
+        // 양방향 차단 조회
+        List<UserBlock> blocks = userBlockRepository.findBlocksBetween(buyerId, owner.getId());
+
+        boolean buyerBlockedOwner = blocks.stream()
+                .anyMatch(b -> b.getBlocker().getId().equals(buyerId));
+
+        boolean ownerBlockedBuyer = blocks.stream()
+                .anyMatch(b -> b.getBlocker().getId().equals(owner.getId()));
+
+        if (buyerBlockedOwner) {
+            log.warn("[거래 기반 채팅방 생성/조회] 차단된 사용자와는 채팅 할 수 없습니다.");
+            throw new CustomException(ChatErrorCode.CHAT_BLOCKED);
+        }
+
+        // 채팅방 find or create
+        ChatRoom chatRoom = findOrCreateChatRoom(itemId, owner, buyerId, item, buyer);
+
+        // product 조회 (상태 무관 — 거래 성사 후이므로 SOLD 포함 허용)
+        Product product = productRepository.findByItemId(itemId).orElse(null);
+
+        Long purchaseIntentId = (product == null) ? null : purchaseIntentRepository
+                .findIdByBuyerIdAndSellerIdAndProductIdAndStatus(buyerId, owner.getId(), product.getId(), PurchaseIntentStatus.SENT)
+                .orElse(null);
+
+        Long sentPurchaseOfferId = purchaseOfferRepository
+                .findIdByProposerIdAndOwnerIdAndItemIdAndStatus(buyerId, owner.getId(), itemId, SENT)
+                .orElse(null);
+
+        Integer offerPrice = purchaseOfferRepository
+                .findOfferPriceByProposerIdAndOwnerIdAndItemIdAndStatusIn(buyerId, owner.getId(), itemId, List.of(SENT, ACCEPTED))
+                .orElse(null);
+
+        return ChatRoomResponse
+                .from(chatRoom, item, product, currentUserId, tradeId, purchaseIntentId, sentPurchaseOfferId, ownerBlockedBuyer, false, offerPrice);
+    }
+
+    // 기존 채팅방이 있으면 반환, 없으면 생성
+    private @NonNull ChatRoom findOrCreateChatRoom(Long itemId, User owner, Long buyerId, Item item, User buyer) {
+        ChatRoom chatRoom;
+        try {
+            chatRoom = chatRoomRepository.findByItemIdAndSellerIdAndBuyerIdAndIsClosedFalse(itemId, owner.getId(), buyerId)
+                    .orElseGet(() -> createChatRoom(item, buyer, owner));
+        } catch (DataIntegrityViolationException e) {
+            chatRoom = chatRoomRepository.findByItemIdAndSellerIdAndBuyerIdAndIsClosedFalse(itemId, owner.getId(), buyerId)
+                    .orElseThrow(() -> {
+                        log.warn("[거래 기반 채팅방 생성/조회] 채팅방을 찾을 수 없습니다. itemId = {}, ownerId = {}, buyerId = {}", itemId, owner.getId(), buyerId);
+                        return new CustomException(ChatErrorCode.CHAT_ROOM_NOT_FOUND);
+                    });
+        }
+        return chatRoom;
+    }
+
     // 채팅방 목록 조회
     public ChatRoomListCursorResponse chatRoomList(Long currentUserId, ChatRoomFilterType type,
                              LocalDateTime cursor, LocalDateTime createdAtCursor, Long cursorId, int size)
diff --git a/src/main/java/com/tenure/domain/trade/repository/TradeRepository.java b/src/main/java/com/tenure/domain/trade/repository/TradeRepository.java
index 379cf296..8fd71e56 100644
--- a/src/main/java/com/tenure/domain/trade/repository/TradeRepository.java
+++ b/src/main/java/com/tenure/domain/trade/repository/TradeRepository.java
@@ -190,4 +190,14 @@ List<Trade> findAllBySourceTypeAndSourceIdIn(
     boolean existsByItemIdAndStatusNotIn(Long itemId, Collection<TradeStatus> statuses);
 
     Optional<Trade> findByItemId(Long itemId);
+
+    @Query("""
+            select trade
+            from Trade trade
+            join fetch trade.buyer
+            join fetch trade.seller
+            join fetch trade.item
+            where trade.id = :tradeId
+            """)
+    Optional<Trade> findByIdWithParticipants(@Param("tradeId") Long tradeId);
 }