diff --git a/src/main/java/com/cmc/mercury/domain/memo/controller/MemoController.java b/src/main/java/com/cmc/mercury/domain/memo/controller/MemoController.java
new file mode 100644
index 0000000..0956b7f
--- /dev/null
+++ b/src/main/java/com/cmc/mercury/domain/memo/controller/MemoController.java
@@ -0,0 +1,59 @@
+package com.cmc.mercury.domain.memo.controller;
+
+import com.cmc.mercury.domain.memo.dto.MemoCreateRequest;
+import com.cmc.mercury.domain.memo.dto.MemoResponse;
+import com.cmc.mercury.domain.memo.dto.MemoUpdateRequest;
+import com.cmc.mercury.domain.memo.service.MemoService;
+import com.cmc.mercury.global.response.SuccessResponse;
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.tags.Tag;
+import jakarta.validation.Valid;
+import lombok.RequiredArgsConstructor;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.HashMap;
+
+@RestController
+@RequestMapping("/records/{recordId}/memos")
+@RequiredArgsConstructor
+@Tag(name = "MemoController", description = "메모 관련 API")
+public class MemoController {
+
+    private final MemoService memoService;
+
+    @PostMapping
+    @Operation(summary = "메모 추가", description = "메모를 생성합니다.")
+    public SuccessResponse<MemoResponse> createMemo(
+            @RequestParam("userId") Long testUserId,
+            @PathVariable Long recordId,
+            @RequestBody @Valid MemoCreateRequest request
+    ) {
+        return SuccessResponse.created(
+                memoService.createMemo(testUserId, recordId, request)
+        );
+    }
+
+    @PatchMapping("/{memoId}")
+    @Operation(summary = "메모 수정", description = "특정 메모를 수정합니다.")
+    public SuccessResponse<MemoResponse> updateMemo(
+            @RequestParam("userId") Long testUserId,
+            @PathVariable Long recordId,
+            @PathVariable Long memoId,
+            @RequestBody MemoUpdateRequest request
+    ) {
+        return SuccessResponse.ok(
+                memoService.updateMemo(testUserId, recordId, memoId, request)
+        );
+    }
+
+    @DeleteMapping("/{memoId}")
+    @Operation(summary = "메모 삭제", description = "특정 메모를 삭제합니다.")
+    public SuccessResponse<?> deleteMemo(
+            @RequestParam("userId") Long testUserId,
+            @PathVariable Long recordId,
+            @PathVariable Long memoId
+    ) {
+        memoService.deleteMemo(testUserId, recordId, memoId);
+        return SuccessResponse.ok(new HashMap<>());
+    }
+}
diff --git a/src/main/java/com/cmc/mercury/domain/memo/service/MemoService.java b/src/main/java/com/cmc/mercury/domain/memo/service/MemoService.java
new file mode 100644
index 0000000..e33baef
--- /dev/null
+++ b/src/main/java/com/cmc/mercury/domain/memo/service/MemoService.java
@@ -0,0 +1,100 @@
+package com.cmc.mercury.domain.memo.service;
+
+import com.cmc.mercury.domain.memo.dto.MemoCreateRequest;
+import com.cmc.mercury.domain.memo.dto.MemoResponse;
+import com.cmc.mercury.domain.memo.dto.MemoUpdateRequest;
+import com.cmc.mercury.domain.memo.entity.Memo;
+import com.cmc.mercury.domain.memo.repository.MemoRepository;
+import com.cmc.mercury.domain.record.entity.Record;
+import com.cmc.mercury.domain.record.entity.RecordDetail;
+import com.cmc.mercury.domain.record.repository.RecordRepository;
+import com.cmc.mercury.global.exception.CustomException;
+import com.cmc.mercury.global.exception.ErrorCode;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class MemoService {
+
+    private final MemoRepository memoRepository;
+    private final RecordRepository recordRepository;
+
+    @Transactional
+    public MemoResponse createMemo(Long testUserId, Long recordId, MemoCreateRequest request) {
+
+        // Record와 RecordDetail을 함께 조회 (Record가 없으면 RecordDetail도 없음)
+        Record record = recordRepository.findByIdAndUser_TestUserId(recordId, testUserId)
+                .orElseThrow(() -> new CustomException(ErrorCode.RECORD_NOT_FOUND));
+
+        RecordDetail recordDetail = record.getRecordDetail();
+
+        // Memo 생성 (아직 연관관계 설정 전)
+        Memo memo = Memo.builder()
+                .content(request.content())
+                .gauge(request.gauge())
+                .build();
+
+        // 연관관계 설정
+        recordDetail.addMemo(memo);
+
+        // 메모의 gauge로 RecordDetail의 updatedGauge 업데이트
+        recordDetail.updateGauge(request.gauge());
+
+        Memo savedMemo = memoRepository.save(memo);
+
+        // save()로 인해 즉시 updatedAt 설정됨 => flush 필요없음
+        // 메모의 updatedAt으로 record와 recordDetail 업데이트
+        record.updateLastModifiedDateWithDetail(savedMemo.getUpdatedAt());
+
+        return MemoResponse.from(savedMemo, recordId);
+
+    }
+
+    @Transactional
+    public MemoResponse updateMemo(Long testUserId, Long recordId, Long memoId, MemoUpdateRequest request) {
+
+        Memo memo = validateAndGetMemo(testUserId, recordId, memoId);
+
+        memo.updateContent(request.content());
+
+        // db에 updatedAt이 바로 반영되어 응답하도록
+        memoRepository.flush();
+
+        Record record = memo.getRecordDetail().getRecord();
+        record.updateLastModifiedDateWithDetail(memo.getUpdatedAt());
+
+        return MemoResponse.from(memo, recordId);
+    }
+
+    @Transactional
+    public void deleteMemo(Long testUserId, Long recordId, Long memoId) {
+
+        Memo memo = validateAndGetMemo(testUserId, recordId, memoId);
+
+        memo.getRecordDetail().getMemos().remove(memo);
+
+        memoRepository.delete(memo);
+    }
+
+    private Memo validateAndGetMemo(Long testUserId, Long recordId, Long memoId) {
+
+        // Record와 RecordDetail을 함께 조회 (Record가 없으면 RecordDetail도 없음)
+        Record record = recordRepository.findByIdAndUser_TestUserId(recordId, testUserId)
+                .orElseThrow(() -> new CustomException(ErrorCode.RECORD_NOT_FOUND));
+
+        RecordDetail recordDetail = record.getRecordDetail();
+
+        Memo memo = memoRepository.findById(memoId)
+                .orElseThrow(() -> new CustomException(ErrorCode.MEMO_NOT_FOUND));
+
+        if (!memo.getRecordDetail().getId().equals(recordDetail.getId())) {
+            throw new CustomException(ErrorCode.MEMO_NOT_BELONG_TO_RECORD);
+        }
+
+        return memo;
+    }
+}