diff --git a/hwe/sammo/API/Message/DecideMessageResponse.php b/hwe/sammo/API/Message/DecideMessageResponse.php
new file mode 100644
index 00000000..b4d4f3c2
--- /dev/null
+++ b/hwe/sammo/API/Message/DecideMessageResponse.php
@@ -0,0 +1,61 @@
+<?php
+
+namespace sammo\API\Message;
+
+use sammo\Session;
+use DateTimeInterface;
+use sammo\DB;
+use sammo\DiplomaticMessage;
+use sammo\KVStorage;
+use sammo\Message;
+use sammo\Validator;
+
+class DecideMessageResponse extends \sammo\BaseAPI
+{
+  public function validateArgs(): ?string
+  {
+    $v = new Validator($this->args);
+    $v->rule('required', ['msgID', 'response']);
+    $v->rule('integer', 'msgID')
+      ->rule('boolean', 'response');
+    if (!$v->validate()) {
+      return $v->errorStr();
+    }
+    $this->args['msgID'] = (int)($this->args['msgID'] ?? -1);
+
+    return null;
+  }
+
+  public function getRequiredSessionMode(): int
+  {
+    return static::REQ_GAME_LOGIN;
+  }
+
+  public function launch(Session $session, ?DateTimeInterface $modifiedSince, ?string $reqEtag)
+  {
+    $msgID = $this->args['msgID'];
+    $msgResponse = $this->args['response'];
+
+    $generalID = $session->generalID;
+
+    $msg = Message::getMessageByID($msgID);
+    if ($msg === null) {
+      return '존재하지 않는 메시지입니다.';
+    }
+
+    $reason = 'success';
+    $gameStor = KVStorage::getStorage(DB::db(), 'game_env');
+    $gameStor->cacheAll();
+    if ($msgResponse) {
+      $result = $msg->agreeMessage($generalID, $reason);
+    } else {
+      $result = $msg->declineMessage($generalID, $reason);
+    }
+
+
+    return [
+      'result' => $result !== DiplomaticMessage::INVALID,
+      'reason' => $reason
+    ];
+  }
+}
diff --git a/hwe/ts/SammoAPI.ts b/hwe/ts/SammoAPI.ts
index 7d9f5e22..eea6bb06 100644
--- a/hwe/ts/SammoAPI.ts
+++ b/hwe/ts/SammoAPI.ts
@@ -175,6 +175,10 @@ const apiRealPath = {
     DeleteMessage: PATCH as APICallT<{
       msgID: number,
     }>,
+    DecideMessageResponse: POST as APICallT<{
+      msgID: number,
+      response: boolean,
+    }>,
     GetContactList: GET as APICallT<undefined, MabilboxListResponse>,
     GetRecentMessage: GET as APICallT<{
       sequence?: number;