diff --git a/src/main/kotlin/com/didit/application/achievement/MissionQueryService.kt b/src/main/kotlin/com/didit/application/achievement/MissionQueryService.kt
index 8556caf4..93670291 100644
--- a/src/main/kotlin/com/didit/application/achievement/MissionQueryService.kt
+++ b/src/main/kotlin/com/didit/application/achievement/MissionQueryService.kt
@@ -5,7 +5,6 @@ import com.didit.application.achievement.dto.MissionInfo
 import com.didit.application.achievement.dto.PopupStatus
 import com.didit.application.achievement.dto.WeeklyStatus
 import com.didit.application.achievement.exception.CurrentMissionNotFoundException
-import com.didit.application.achievement.exception.MissionDefinitionNotFoundException
 import com.didit.application.achievement.exception.UserLevelNotFoundException
 import com.didit.application.achievement.provided.MissionFinder
 import com.didit.application.achievement.required.MissionRepository
@@ -34,11 +33,21 @@ class MissionQueryService(
 ) : MissionFinder {
     override fun getCurrentMission(userId: UUID): CurrentMissionResponse {
         val userLevel = userLevelRepository.findByUserId(userId) ?: throw UserLevelNotFoundException(userId)
+        val missionLevel = userLevel.currentLevel + 1
+        val mission = missionRepository.findByLevel(missionLevel)
+
+        if (mission == null) {
+            val lastMission = userMissionRepository.findByUserId(userId).firstOrNull()
+            return CurrentMissionResponse(
+                currentLevel = userLevel.currentLevel,
+                mission = null,
+                weeklyStatus = buildWeeklyStatusForUser(userId),
+                popup = lastMission?.let { getPopupStatus(it) } ?: PopupStatus(exists = false, type = null),
+            )
+        }
+
         val userMission =
             userMissionRepository.findCurrentMissionByUserId(userId) ?: throw CurrentMissionNotFoundException(userId)
-        val missionLevel = userLevel.currentLevel + 1
-        val mission =
-            missionRepository.findByLevel(missionLevel) ?: throw MissionDefinitionNotFoundException(missionLevel)
 
         val missionInfo =
             MissionInfo(
@@ -86,7 +95,10 @@ class MissionQueryService(
         if (mission.missionType != MissionType.CONSECUTIVE_WEEK) {
             return null
         }
+        return buildWeeklyStatusForUser(userId)
+    }
 
+    private fun buildWeeklyStatusForUser(userId: UUID): WeeklyStatus {
         val weekStartDate = getWeekStartDate(ServiceTime.today())
         val from = ServiceTime.startOfDayUtc(weekStartDate)
         val to = ServiceTime.startOfDayUtc(weekStartDate.plusWeeks(1))
diff --git a/src/main/kotlin/com/didit/application/achievement/UserMissionService.kt b/src/main/kotlin/com/didit/application/achievement/UserMissionService.kt
index a5b433f8..bfdf919d 100644
--- a/src/main/kotlin/com/didit/application/achievement/UserMissionService.kt
+++ b/src/main/kotlin/com/didit/application/achievement/UserMissionService.kt
@@ -35,6 +35,7 @@ class UserMissionService(
     override fun confirmLevelUp(userId: UUID) {
         val userMission =
             userMissionRepository.findCurrentMissionByUserId(userId)
+                ?: userMissionRepository.findByUserId(userId).firstOrNull()
                 ?: throw CurrentMissionNotFoundException(userId)
 
         userMission.levelUpPopupShown = true
diff --git a/src/main/kotlin/com/didit/application/achievement/dto/CurrentMissionResponse.kt b/src/main/kotlin/com/didit/application/achievement/dto/CurrentMissionResponse.kt
index d2e2b0d6..2a8ddbcd 100644
--- a/src/main/kotlin/com/didit/application/achievement/dto/CurrentMissionResponse.kt
+++ b/src/main/kotlin/com/didit/application/achievement/dto/CurrentMissionResponse.kt
@@ -2,7 +2,7 @@ package com.didit.application.achievement.dto
 
 data class CurrentMissionResponse(
     val currentLevel: Int,
-    val mission: MissionInfo,
+    val mission: MissionInfo?,
     val weeklyStatus: WeeklyStatus?,
     val popup: PopupStatus,
 )
diff --git a/src/test/kotlin/com/didit/application/achievement/MissionQueryServiceTest.kt b/src/test/kotlin/com/didit/application/achievement/MissionQueryServiceTest.kt
index 2866ede5..97bd509b 100644
--- a/src/test/kotlin/com/didit/application/achievement/MissionQueryServiceTest.kt
+++ b/src/test/kotlin/com/didit/application/achievement/MissionQueryServiceTest.kt
@@ -1,7 +1,6 @@
 package com.didit.application.achievement
 
 import com.didit.application.achievement.exception.CurrentMissionNotFoundException
-import com.didit.application.achievement.exception.MissionDefinitionNotFoundException
 import com.didit.application.achievement.exception.UserLevelNotFoundException
 import com.didit.application.achievement.required.MissionRepository
 import com.didit.application.achievement.required.UserLevelRepository
@@ -74,10 +73,10 @@ class MissionQueryServiceTest {
         val result = missionQueryService.getCurrentMission(userId)
 
         assertThat(result.currentLevel).isEqualTo(0)
-        assertThat(result.mission.type).isEqualTo("FIRST_RETRO")
-        assertThat(result.mission.progress).isEqualTo(0)
-        assertThat(result.mission.target).isEqualTo(1)
-        assertThat(result.mission.remainingDays).isNull()
+        assertThat(result.mission!!.type).isEqualTo("FIRST_RETRO")
+        assertThat(result.mission!!.progress).isEqualTo(0)
+        assertThat(result.mission!!.target).isEqualTo(1)
+        assertThat(result.mission!!.remainingDays).isNull()
         assertThat(result.weeklyStatus).isNull()
         assertThat(result.popup.exists).isFalse()
     }
@@ -103,8 +102,8 @@ class MissionQueryServiceTest {
         val result = missionQueryService.getCurrentMission(userId)
 
         assertThat(result.currentLevel).isEqualTo(1)
-        assertThat(result.mission.type).isEqualTo("TIME_LIMITED")
-        assertThat(result.mission.remainingDays).isEqualTo(5)
+        assertThat(result.mission!!.type).isEqualTo("TIME_LIMITED")
+        assertThat(result.mission!!.remainingDays).isEqualTo(5)
         assertThat(result.weeklyStatus).isNull()
     }
 
@@ -130,7 +129,7 @@ class MissionQueryServiceTest {
         val result = missionQueryService.getCurrentMission(userId)
 
         assertThat(result.currentLevel).isEqualTo(2)
-        assertThat(result.mission.type).isEqualTo("CONSECUTIVE_WEEK")
+        assertThat(result.mission!!.type).isEqualTo("CONSECUTIVE_WEEK")
         assertThat(result.weeklyStatus).isNotNull()
         assertThat(result.weeklyStatus!!.days).hasSize(7)
     }
@@ -147,6 +146,7 @@ class MissionQueryServiceTest {
     fun `현재 미션이 없으면 CurrentMissionNotFoundException을 발생시킨다`() {
         val userLevel = UserLevel(userId = userId, currentLevel = 1)
         whenever(userLevelRepository.findByUserId(userId)).thenReturn(userLevel)
+        whenever(missionRepository.findByLevel(2)).thenReturn(Mission.timeLimited())
         whenever(userMissionRepository.findCurrentMissionByUserId(userId)).thenReturn(null)
 
         assertThatThrownBy { missionQueryService.getCurrentMission(userId) }
@@ -154,16 +154,23 @@ class MissionQueryServiceTest {
     }
 
     @Test
-    fun `미션 정의가 없으면 MissionDefinitionNotFoundException을 발생시킨다`() {
-        val userLevel = UserLevel(userId = userId, currentLevel = 0)
-        val userMission = UserMission(userId = userId, missionId = UUID.randomUUID())
+    fun `최고 레벨(미션 정의 없음)이면 mission이 null이고 주간 현황을 반환한다`() {
+        val userLevel = UserLevel(userId = userId, currentLevel = 10)
 
         whenever(userLevelRepository.findByUserId(userId)).thenReturn(userLevel)
-        whenever(userMissionRepository.findCurrentMissionByUserId(userId)).thenReturn(userMission)
-        whenever(missionRepository.findByLevel(1)).thenReturn(null)
+        whenever(missionRepository.findByLevel(11)).thenReturn(null)
+        whenever(userMissionRepository.findByUserId(userId)).thenReturn(emptyList())
+        whenever(retrospectiveRepository.findCompletedByUserIdAndPeriod(eq(userId), any(), any())).thenReturn(
+            emptyList(),
+        )
 
-        assertThatThrownBy { missionQueryService.getCurrentMission(userId) }
-            .isInstanceOf(MissionDefinitionNotFoundException::class.java)
+        val result = missionQueryService.getCurrentMission(userId)
+
+        assertThat(result.currentLevel).isEqualTo(10)
+        assertThat(result.mission).isNull()
+        assertThat(result.weeklyStatus).isNotNull()
+        assertThat(result.weeklyStatus!!.days).hasSize(7)
+        assertThat(result.popup.exists).isFalse()
     }
 
     @Test