diff --git a/core/domain/src/main/kotlin/com/idle/domain/usecase/chatting/GetChatRoomListUseCase.kt b/core/domain/src/main/kotlin/com/idle/domain/usecase/chatting/GetChatRoomListUseCase.kt
index 9ba7c408..59c0c1cf 100644
--- a/core/domain/src/main/kotlin/com/idle/domain/usecase/chatting/GetChatRoomListUseCase.kt
+++ b/core/domain/src/main/kotlin/com/idle/domain/usecase/chatting/GetChatRoomListUseCase.kt
@@ -15,7 +15,7 @@ class GetChatRoomListUseCase @Inject constructor(
                 createdAt = LocalDateTime.now().minusDays(1),
                 lastMessage = "안녕하세요!안녕하세요!안녕하세요!안녕하세요!안녕하세요!안녕하세요!",
                 lastSentAt = LocalDateTime.now().minusHours(1),
-                unReadMessageCount = 3,
+                unReadMessageCount = 99,
                 profileImageUrl = "",
             ),
             ChatRoom(
@@ -25,7 +25,7 @@ class GetChatRoomListUseCase @Inject constructor(
                 createdAt = LocalDateTime.now().minusDays(3),
                 lastMessage = "오늘 만날 수 있을까요?",
                 lastSentAt = LocalDateTime.now().minusHours(5),
-                unReadMessageCount = 99,
+                unReadMessageCount = 100,
                 profileImageUrl = "",
             ),
             ChatRoom(
diff --git a/core/domain/src/main/kotlin/com/idle/domain/util/NumberUtil.kt b/core/domain/src/main/kotlin/com/idle/domain/util/NumberUtil.kt
index 3b9f6768..fb98ba0d 100644
--- a/core/domain/src/main/kotlin/com/idle/domain/util/NumberUtil.kt
+++ b/core/domain/src/main/kotlin/com/idle/domain/util/NumberUtil.kt
@@ -39,4 +39,12 @@ fun formatBusinessRegistrationNumber(businessRegistrationNumber: String): String
 
         else -> throw IllegalArgumentException("사업자 등록번호 형식이 맞지 않습니다.")
     }
+}
+
+fun Int.formatUnReadNumber(): String {
+    return when {
+        this < 0 -> "0"
+        this >= 100 -> "99+"
+        else -> this.toString()
+    }
 }
\ No newline at end of file
diff --git a/core/domain/src/test/kotlin/com/idle/domain/util/NumberUtilTest.kt b/core/domain/src/test/kotlin/com/idle/domain/util/NumberUtilTest.kt
index fc376ab8..9caea9ed 100644
--- a/core/domain/src/test/kotlin/com/idle/domain/util/NumberUtilTest.kt
+++ b/core/domain/src/test/kotlin/com/idle/domain/util/NumberUtilTest.kt
@@ -118,4 +118,40 @@ class NumberUtilTest {
             formatBusinessRegistrationNumber(businessRegistrationNumber)
         }
     }
+
+    @Test
+    fun `음수일 경우 0으로 반환된다`() {
+        // Given
+        val number = -5
+
+        // When
+        val result = number.formatUnReadNumber()
+
+        // Then
+        assertEquals("0", result)
+    }
+
+    @Test
+    fun `99 이하의 숫자는 그대로 문자열로 반환된다`() {
+        // Given
+        val number = 99
+
+        // When
+        val result = number.formatUnReadNumber()
+
+        // Then
+        assertEquals("99", result)
+    }
+
+    @Test
+    fun `100 이상의 숫자는 '99+'로 반환된다`() {
+        // Given
+        val number = 100
+
+        // When
+        val result = number.formatUnReadNumber()
+
+        // Then
+        assertEquals("99+", result)
+    }
 }
\ No newline at end of file
diff --git a/feature/center/chatting/src/main/java/com/idle/center/chatting/CenterChattingFragment.kt b/feature/center/chatting/src/main/java/com/idle/center/chatting/CenterChattingFragment.kt
index fb028c4f..9dd67531 100644
--- a/feature/center/chatting/src/main/java/com/idle/center/chatting/CenterChattingFragment.kt
+++ b/feature/center/chatting/src/main/java/com/idle/center/chatting/CenterChattingFragment.kt
@@ -44,6 +44,7 @@ import com.idle.designsystem.compose.foundation.CareTheme
 import com.idle.domain.model.auth.UserType
 import com.idle.domain.model.chatting.ChatRoom
 import com.idle.domain.util.formatRelativeDateTime
+import com.idle.domain.util.formatUnReadNumber
 import dagger.hilt.android.AndroidEntryPoint
 
 @AndroidEntryPoint
@@ -234,7 +235,7 @@ internal fun ChatRoomItem(
                     ) {
                         Text(
                             text = if (chatRoom.unReadMessageCount != 0)
-                                chatRoom.unReadMessageCount.toString() else "",
+                                chatRoom.unReadMessageCount.formatUnReadNumber() else "",
                             style = CareTheme.typography.caption1.copy(fontWeight = FontWeight.Bold),
                             color = CareTheme.colors.white000,
                             textAlign = TextAlign.Center,
diff --git a/feature/worker/chatting/src/main/java/com/idle/worker/chatting/WorkerChattingFragment.kt b/feature/worker/chatting/src/main/java/com/idle/worker/chatting/WorkerChattingFragment.kt
index 8ff0a0a6..62066807 100644
--- a/feature/worker/chatting/src/main/java/com/idle/worker/chatting/WorkerChattingFragment.kt
+++ b/feature/worker/chatting/src/main/java/com/idle/worker/chatting/WorkerChattingFragment.kt
@@ -47,6 +47,7 @@ import com.idle.designsystem.compose.foundation.CareTheme
 import com.idle.domain.model.auth.UserType
 import com.idle.domain.model.chatting.ChatRoom
 import com.idle.domain.util.formatRelativeDateTime
+import com.idle.domain.util.formatUnReadNumber
 import dagger.hilt.android.AndroidEntryPoint
 
 @AndroidEntryPoint
@@ -239,7 +240,7 @@ internal fun ChatRoomItem(
                     ) {
                         Text(
                             text = if (chatRoom.unReadMessageCount != 0)
-                                chatRoom.unReadMessageCount.toString() else "",
+                                chatRoom.unReadMessageCount.formatUnReadNumber() else "",
                             style = CareTheme.typography.caption1.copy(fontWeight = FontWeight.Bold),
                             color = CareTheme.colors.white000,
                             textAlign = TextAlign.Center,