diff --git a/app/src/main/java/com/example/tampopo_client/views/ChatActivity.java b/app/src/main/java/com/example/tampopo_client/views/ChatActivity.java
index 494c624..00f42a4 100644
--- a/app/src/main/java/com/example/tampopo_client/views/ChatActivity.java
+++ b/app/src/main/java/com/example/tampopo_client/views/ChatActivity.java
@@ -20,10 +20,12 @@
 import com.example.tampopo_client.Tampopo;
 import com.example.tampopo_client.viewmodels.ChatViewModel;
 import com.example.tampopo_client.viewmodels.ChatViewModelFactory;
+import com.example.tampopo_client.viewmodels.UserViewModel;
 
 public class ChatActivity extends AppCompatActivity {
 
   private ChatViewModel chatViewModel;
+  private UserViewModel userViewModel;
 
   //メンバー変数
   private EditText senderMessage;
@@ -47,6 +49,7 @@
     ChatViewModelFactory factory1 = new ChatViewModelFactory(tampopo.getUserId(), tampopo.getToken());
     chatViewModel = new ViewModelProvider(this, factory1).get(ChatViewModel.class);
     chatViewModel.setChatRoomId(tampopo.getChatroomId());
+    userViewModel = new ViewModelProvider(this).get(UserViewModel.class);
 
     senderMessage = findViewById(R.id.sender_message);
     receiverMessage = findViewById(R.id.receiver_message);
@@ -54,7 +57,19 @@
     backButton = findViewById(R.id.back_Button);
     roomId = findViewById(R.id.chat_room_id);
     TextView friendIdTextView = findViewById(R.id.friend_id);
-    friendIdTextView.setText(tampopo.getChatFriendId());
+    // ひとまずIDを暫定表示
+    String chatFriendId = tampopo.getChatFriendId();
+    friendIdTextView.setText(chatFriendId);
+    // 相手のニックネームを取得して表示（最小変更のため同期APIを別スレッドで呼び出し）
+    new Thread(() -> {
+      try {
+        String nickname = userViewModel.getNickname(chatFriendId);
+        String display = (nickname != null && !nickname.isEmpty()) ? nickname : chatFriendId;
+        runOnUiThread(() -> friendIdTextView.setText(display));
+      } catch (Exception e) {
+        // 失敗時はIDのまま
+      }
+    }).start();
     receiverMessage.setKeyListener(null);//受信メッセージ編集不可
 
 //    buttonSend.setOnClickListener(new OnClickListener() {