diff --git a/MMOTestServer/MMOserver/Game/GameServer.cs b/MMOTestServer/MMOserver/Game/GameServer.cs
index 5fa6e92..c88cfb2 100644
--- a/MMOTestServer/MMOserver/Game/GameServer.cs
+++ b/MMOTestServer/MMOserver/Game/GameServer.cs
@@ -1269,7 +1269,7 @@ public class GameServer : ServerBase
         {
             Log.Warning("[GameServer] INTO_BOSS_RAID 파티 없음 HashKey={Key}", hashKey);
             SendTo(peer, PacketSerializer.Serialize((ushort)PacketCode.INTO_BOSS_RAID,
-                new IntoBossRaidPacket { RaidId = packet.RaidId, IsSuccess = false }));
+                new IntoBossRaidPacket { RaidId = packet.RaidId, IsSuccess = false, Reason = "파티에 속해있지 않습니다." }));
             return;
         }
 
@@ -1278,7 +1278,7 @@ public class GameServer : ServerBase
         {
             Log.Warning("[GameServer] INTO_BOSS_RAID 파티장 아님 HashKey={Key} LeaderId={LeaderId}", hashKey, party.LeaderId);
             SendTo(peer, PacketSerializer.Serialize((ushort)PacketCode.INTO_BOSS_RAID,
-                new IntoBossRaidPacket { RaidId = packet.RaidId, IsSuccess = false }));
+                new IntoBossRaidPacket { RaidId = packet.RaidId, IsSuccess = false, Reason = "파티장만 보스 레이드를 시작할 수 있습니다." }));
             return;
         }
 
@@ -1303,7 +1303,7 @@ public class GameServer : ServerBase
             {
                 SendTo(peer,
                     PacketSerializer.Serialize((ushort)PacketCode.INTO_BOSS_RAID,
-                        new IntoBossRaidPacket { RaidId = -1, IsSuccess = false }));
+                        new IntoBossRaidPacket { RaidId = -1, IsSuccess = false, Reason = "보스 레이드 방을 배정받지 못했습니다. 잠시 후 다시 시도해주세요." }));
 
                 Log.Debug("[GameServer] INTO_BOSS_RAID HashKey={Key} PartyId={PartyId} AssignedRaidMapId={RaidId} Failed", hashKey,
                     party.PartyId, -1);
diff --git a/MMOTestServer/MMOserver/Packet/PacketBody.cs b/MMOTestServer/MMOserver/Packet/PacketBody.cs
index babf7c6..f24c926 100644
--- a/MMOTestServer/MMOserver/Packet/PacketBody.cs
+++ b/MMOTestServer/MMOserver/Packet/PacketBody.cs
@@ -827,6 +827,14 @@ public class IntoBossRaidPacket
         get;
         set;
     }
+
+    // 실패 사유 (서버 -> 클라, IsSuccess == false 시)
+    [ProtoMember(5)]
+    public string Reason
+    {
+        get;
+        set;
+    }
 }
 
 // PARTY_CHANGE_MAP (클라 -> 서버 전용)