diff --git a/src/main/java/com/piuda/callcare/domain/medication/controller/MedicationController.java b/src/main/java/com/piuda/callcare/domain/medication/controller/MedicationController.java
index 3ad7419..a8d03bb 100644
--- a/src/main/java/com/piuda/callcare/domain/medication/controller/MedicationController.java
+++ b/src/main/java/com/piuda/callcare/domain/medication/controller/MedicationController.java
@@ -2,6 +2,7 @@
 
 import com.piuda.callcare.domain.medication.dto.request.MedicationCreateRequest;
 import com.piuda.callcare.domain.medication.dto.request.MedicationUpdateRequest;
+import com.piuda.callcare.domain.medication.dto.response.MedicationDetailResponse;
 import com.piuda.callcare.domain.medication.dto.response.MedicationGroupItemResponse;
 import com.piuda.callcare.domain.medication.dto.response.MedicationNoteGroupResponse;
 import com.piuda.callcare.domain.medication.dto.response.MedicationResponse;
@@ -39,6 +40,18 @@ public ResponseEntity<ApiResponse<List<MedicationResponse>>> registerBatch(
         return ResponseUtils.created(medicationCommandService.registerBatch(userId, requests));
     }
 
+    @Operation(
+        summary = "약 단건 상세 조회",
+        description = "약물노트에서 '재등록' 버튼 클릭 시 호출합니다. 약 이름·복용법·병원명·처방일·메모 등 등록 화면 프리필에 필요한 모든 필드를 반환합니다. 반환된 값을 그대로 POST /api/medications/batch에 담아 재등록하면 됩니다."
+    )
+    @GetMapping("/{medicationId}")
+    public ResponseEntity<ApiResponse<MedicationDetailResponse>> getDetail(
+            @AuthenticationPrincipal Long userId,
+            @PathVariable Long medicationId
+    ) {
+        return ResponseUtils.ok(medicationQueryService.getDetail(userId, medicationId));
+    }
+
     @Operation(summary = "약물노트 그룹 상세 조회", description = "병원+처방일 그룹 카드 클릭 시 해당 그룹의 약 리스트와 각 약의 메모를 반환합니다. hospitalName/prescriptionDate 미전달 시 null 그룹 조회.")
     @GetMapping("/group")
     public ResponseEntity<ApiResponse<List<MedicationGroupItemResponse>>> getGroup(
diff --git a/src/main/java/com/piuda/callcare/domain/medication/converter/MedicationConverter.java b/src/main/java/com/piuda/callcare/domain/medication/converter/MedicationConverter.java
index 83768f3..6d0a75a 100644
--- a/src/main/java/com/piuda/callcare/domain/medication/converter/MedicationConverter.java
+++ b/src/main/java/com/piuda/callcare/domain/medication/converter/MedicationConverter.java
@@ -1,5 +1,6 @@
 package com.piuda.callcare.domain.medication.converter;
 
+import com.piuda.callcare.domain.medication.dto.response.MedicationDetailResponse;
 import com.piuda.callcare.domain.medication.dto.response.MedicationGroupItemResponse;
 import com.piuda.callcare.domain.medication.dto.response.MedicationNoteItemResponse;
 import com.piuda.callcare.domain.medication.dto.response.MedicationResponse;
@@ -31,6 +32,28 @@ public MedicationGroupItemResponse toGroupItemResponse(Medication medication) {
         );
     }
 
+    // Medication → MedicationDetailResponse (약 단건 상세 — 재등록 화면 프리필용)
+    public MedicationDetailResponse toDetailResponse(Medication medication) {
+        return new MedicationDetailResponse(
+                medication.getId(),
+                medication.getDrugName(),
+                medication.getDrugNickname(),
+                medication.getDrugType(),
+                medication.getImageUrl(),
+                medication.getDosagePerTime(),
+                medication.getTimesPerDay(),
+                medication.getTotalDays(),
+                medication.getStartDate(),
+                medication.getEndDate(),
+                medication.getPrescriptionDate(),
+                medication.getHospitalName(),
+                medication.getUsageStorageInfo(),
+                medication.getMemo(),
+                medication.getIsActive(),
+                medication.getDrugInfo() != null ? medication.getDrugInfo().getId() : null
+        );
+    }
+
     // Medication → MedicationNoteItemResponse (약물노트 리스트 카드 내 약 단건)
     public MedicationNoteItemResponse toNoteItemResponse(Medication medication) {
         return new MedicationNoteItemResponse(
diff --git a/src/main/java/com/piuda/callcare/domain/medication/dto/response/MedicationDetailResponse.java b/src/main/java/com/piuda/callcare/domain/medication/dto/response/MedicationDetailResponse.java
new file mode 100644
index 0000000..239baf0
--- /dev/null
+++ b/src/main/java/com/piuda/callcare/domain/medication/dto/response/MedicationDetailResponse.java
@@ -0,0 +1,57 @@
+package com.piuda.callcare.domain.medication.dto.response;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+import java.time.LocalDate;
+
+@Schema(description = "약 단건 상세 응답 — 재등록 화면 프리필용")
+public record MedicationDetailResponse(
+
+        @Schema(description = "약 ID")
+        Long medicationId,
+
+        @Schema(description = "약 이름")
+        String drugName,
+
+        @Schema(description = "약 별명 (없으면 null)")
+        String drugNickname,
+
+        @Schema(description = "약 종류 (없으면 null)")
+        String drugType,
+
+        @Schema(description = "약 이미지 URL (없으면 null)")
+        String imageUrl,
+
+        @Schema(description = "1회 복용량 (예: 1정, 5ml)")
+        String dosagePerTime,
+
+        @Schema(description = "1일 복용 횟수")
+        Integer timesPerDay,
+
+        @Schema(description = "총 복용 일수 (없으면 null)")
+        Integer totalDays,
+
+        @Schema(description = "복용 시작일")
+        LocalDate startDate,
+
+        @Schema(description = "복용 종료일 (없으면 null)")
+        LocalDate endDate,
+
+        @Schema(description = "처방 날짜 (없으면 null)")
+        LocalDate prescriptionDate,
+
+        @Schema(description = "병원명 (없으면 null)")
+        String hospitalName,
+
+        @Schema(description = "복용법 + 보관법 — DrugInfo 연결 시에만 채워짐, 없으면 null")
+        String usageStorageInfo,
+
+        @Schema(description = "사용자 자유 입력 메모 (없으면 null)")
+        String memo,
+
+        @Schema(description = "복용 중 여부 — false면 종료된 약")
+        Boolean isActive,
+
+        @Schema(description = "연결된 DrugInfo ID — 재등록 시 drugInfoId 필드에 그대로 사용 (없으면 null)")
+        Long drugInfoId
+) {}
diff --git a/src/main/java/com/piuda/callcare/domain/medication/service/query/MedicationQueryService.java b/src/main/java/com/piuda/callcare/domain/medication/service/query/MedicationQueryService.java
index d4802e8..81b6ac8 100644
--- a/src/main/java/com/piuda/callcare/domain/medication/service/query/MedicationQueryService.java
+++ b/src/main/java/com/piuda/callcare/domain/medication/service/query/MedicationQueryService.java
@@ -1,6 +1,7 @@
 package com.piuda.callcare.domain.medication.service.query;
 
 import com.piuda.callcare.domain.medication.converter.MedicationConverter;
+import com.piuda.callcare.domain.medication.dto.response.MedicationDetailResponse;
 import com.piuda.callcare.domain.medication.dto.response.MedicationGroupItemResponse;
 import com.piuda.callcare.domain.medication.dto.response.MedicationNoteGroupResponse;
 import com.piuda.callcare.domain.medication.dto.response.MedicationNoteItemResponse;
@@ -28,6 +29,16 @@ public class MedicationQueryService {
     private final SeniorRepository seniorRepository;
     private final MedicationConverter medicationConverter;
 
+    // 약 단건 상세 조회 — 재등록 화면 프리필용
+    public MedicationDetailResponse getDetail(Long userId, Long medicationId) {
+        if (userId == null) throw new CallCareException(ErrorCode.FORBIDDEN);
+        Medication medication = medicationRepository.findById(medicationId)
+                .orElseThrow(() -> new CallCareException(ErrorCode.MEDICATION_NOT_FOUND));
+        seniorRepository.findByIdAndUser_Id(medication.getSenior().getId(), userId)
+                .orElseThrow(() -> new CallCareException(ErrorCode.FORBIDDEN));
+        return medicationConverter.toDetailResponse(medication);
+    }
+
     // 병원+처방일 그룹의 약 상세 목록 조회
     public List<MedicationGroupItemResponse> getGroup(Long userId, Long seniorId, String hospitalName, LocalDate prescriptionDate) {
         if (userId == null) {