diff --git a/oneco/src/main/java/com/oneco/backend/mission/application/port/in/ApproveMissionUseCase.java b/oneco/src/main/java/com/oneco/backend/mission/application/port/in/ApproveMissionUseCase.java
index c22fc84..8d6dd3b 100644
--- a/oneco/src/main/java/com/oneco/backend/mission/application/port/in/ApproveMissionUseCase.java
+++ b/oneco/src/main/java/com/oneco/backend/mission/application/port/in/ApproveMissionUseCase.java
@@ -5,5 +5,6 @@
 
 public interface ApproveMissionUseCase {
 
+	// 미션 수신자는 미션 승인 또는 거절을 결정한다.
 	MissionResult decide(ApproveMissionCommand command);
 }
diff --git a/oneco/src/main/java/com/oneco/backend/mission/application/service/CreateMissionService.java b/oneco/src/main/java/com/oneco/backend/mission/application/service/CreateMissionService.java
index 8d1b7d6..94f8e47 100644
--- a/oneco/src/main/java/com/oneco/backend/mission/application/service/CreateMissionService.java
+++ b/oneco/src/main/java/com/oneco/backend/mission/application/service/CreateMissionService.java
@@ -69,7 +69,7 @@ public MissionResult request(CreateMissionCommand command) {
 		Reward reward = Reward.of(title, command.message());
 
 		// Mission 생성시 필요한 값: FamilyRelationId, CategoryId, Period, Reward(nullable)
-		Mission mission = Mission.create(requesterId, recipientId, relationId, categoryId, period, reward);
+		Mission mission = Mission.of(requesterId, recipientId, relationId, categoryId, period, reward);
 
 		// 3. 저장
 		missionPort.save(mission);
diff --git a/oneco/src/main/java/com/oneco/backend/mission/application/service/MissionApprovalService.java b/oneco/src/main/java/com/oneco/backend/mission/application/service/MissionApprovalService.java
index a0618d9..87aa66d 100644
--- a/oneco/src/main/java/com/oneco/backend/mission/application/service/MissionApprovalService.java
+++ b/oneco/src/main/java/com/oneco/backend/mission/application/service/MissionApprovalService.java
@@ -1,5 +1,7 @@
 package com.oneco.backend.mission.application.service;
 
+import java.time.LocalDate;
+
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
@@ -31,9 +33,20 @@ public MissionResult decide(ApproveMissionCommand command) {
 		MemberId recipientId = MemberId.of(command.recipientId());
 		validateRecipient(mission, recipientId);
 		validateStatus(mission);
+		validateNotExpired(mission);
 
 		if (command.accepted()) {
+			// 미션 승인 상태일 경우
 			mission.acceptApproval();
+
+			// 미션 시작일이 오늘(요청 수락일)과 같거나 이전이라면 즉시 미션 진행 상태로 변경
+			LocalDate startDate = mission.getPeriod().getStartDate();
+			LocalDate today = LocalDate.now();
+
+			if (startDate.isBefore(today) || startDate.isEqual(today)) {
+				mission.markInProgress(); // 미션을 즉시 진행 상태로 변경
+			}
+
 		} else {
 			mission.rejectApproval();
 		}
@@ -44,7 +57,8 @@ public MissionResult decide(ApproveMissionCommand command) {
 
 	private void validateRecipient(Mission mission, MemberId recipientId) {
 		if (!mission.getRecipientId().equals(recipientId)) {
-			throw BaseException.from(MissionErrorCode.MISSION_APPROVAL_FORBIDDEN);
+			throw BaseException.from(MissionErrorCode.MISSION_APPROVAL_FORBIDDEN,
+				"미션 수신자가 아닌 사용자는 승인/거절할 수 없습니다.");
 		}
 	}
 
@@ -54,4 +68,12 @@ private void validateStatus(Mission mission) {
 				"승인/거절은 APPROVAL_REQUEST 상태에서만 가능합니다.");
 		}
 	}
+
+	private void validateNotExpired(Mission mission) {
+		LocalDate today = LocalDate.now();
+		if (today.isAfter(mission.getPeriod().getEndDate())) {
+			throw BaseException.from(MissionErrorCode.LATE_MISSION_APPROVAL,
+				"미션 종료일이 지난 후에는 승인할 수 없습니다.");
+		}
+	}
 }
diff --git a/oneco/src/main/java/com/oneco/backend/mission/application/service/MissionBatchService.java b/oneco/src/main/java/com/oneco/backend/mission/application/service/MissionBatchService.java
index e7b2624..792b826 100644
--- a/oneco/src/main/java/com/oneco/backend/mission/application/service/MissionBatchService.java
+++ b/oneco/src/main/java/com/oneco/backend/mission/application/service/MissionBatchService.java
@@ -80,7 +80,7 @@ public void startScheduledMissions() {
 		long successCount = 0; // 성공 처리 건수
 		long errorCount = 0; // 실패 처리 중 오류 발생 건수
 
-		// 1. 오늘이 시작일인 미션들을 조회한다.
+		// 1. 오늘이 시작일이면서 미션 상태가 APPROVAL_ACCEPTED인 미션들을 조회한다.
 		List<Mission> missionsToStart = missionPort.findAllMissionsStartingToday(today);
 
 		// =============================
diff --git a/oneco/src/main/java/com/oneco/backend/mission/domain/exception/MissionErrorCode.java b/oneco/src/main/java/com/oneco/backend/mission/domain/exception/MissionErrorCode.java
index c2e5838..b4a3530 100644
--- a/oneco/src/main/java/com/oneco/backend/mission/domain/exception/MissionErrorCode.java
+++ b/oneco/src/main/java/com/oneco/backend/mission/domain/exception/MissionErrorCode.java
@@ -120,6 +120,11 @@ public enum MissionErrorCode implements ErrorCode {
 		HttpStatus.BAD_REQUEST,
 		"미션 ID가 유효하지 않습니다.",
 		"MISSION_ERROR_400_INVALID_MISSION_ID"
+	),
+	LATE_MISSION_APPROVAL(
+		HttpStatus.BAD_REQUEST,
+		"미션 종료일이 지난 후에는 승인할 수 없습니다.",
+		"MISSION_ERROR_400_LATE_MISSION_APPROVAL"
 	);
 
 	private final HttpStatus httpStatus;
diff --git a/oneco/src/main/java/com/oneco/backend/mission/domain/mission/Mission.java b/oneco/src/main/java/com/oneco/backend/mission/domain/mission/Mission.java
index 3a4b43c..11ba99b 100644
--- a/oneco/src/main/java/com/oneco/backend/mission/domain/mission/Mission.java
+++ b/oneco/src/main/java/com/oneco/backend/mission/domain/mission/Mission.java
@@ -106,7 +106,7 @@ private Mission(
 	}
 
 	// 미션 생성 메서드
-	public static Mission create(
+	public static Mission of(
 		MemberId requesterId,
 		MemberId recipientId,
 		FamilyRelationId familyRelationId,
diff --git a/oneco/src/main/java/com/oneco/backend/mission/presentation/MissionController.java b/oneco/src/main/java/com/oneco/backend/mission/presentation/MissionController.java
index df77f71..8ee06d0 100644
--- a/oneco/src/main/java/com/oneco/backend/mission/presentation/MissionController.java
+++ b/oneco/src/main/java/com/oneco/backend/mission/presentation/MissionController.java
@@ -75,8 +75,10 @@ public ResponseEntity<DataResponse<MissionResult>> createMission(
 		description = """
 			- 미션 승인 또는 거절 요청을 처리한다.
 			- 미션 수신자는 미션을 승인하거나 거절할 수 있다.
-			- 승인 시 미션 상태는 '진행중'으로 변경된다.
+			- 승인 시 미션 상태는 '승인 수락'으로 변경된다.
 			- 거절 시 미션 상태는 '거절됨'으로 변경된다.
+			- 미션 승인 시점이 미션 시작일이과 같을 경우 미션 상태는 즉시 '진행중'으로 변경된다.
+			- 미션 승인 시점이 미션 시작일보다 이후 일 경우 미션 상태는 즉시 '진행중'으로 변경된다.
 			"""
 	)
 	@ApiResponses({