diff --git a/backend/src/app.module.ts b/backend/src/app.module.ts
index 1c34f76..f925796 100644
--- a/backend/src/app.module.ts
+++ b/backend/src/app.module.ts
@@ -8,6 +8,7 @@ import { GameModule } from './game/game.module';
 import { LikeModule } from './like/like.module';
 import { CommentModule } from './comment/comment.module';
 import { UserModule } from './user/user.module';
+import { SelectedItemModule } from './selected-item/selected-item.module';
 
 @Module({
   imports: [
@@ -24,6 +25,7 @@ import { UserModule } from './user/user.module';
     LikeModule,
     CommentModule,
     UserModule,
+    SelectedItemModule,
   ],
   controllers: [],
   providers: [],
diff --git a/backend/src/comment/comment.controller.ts b/backend/src/comment/comment.controller.ts
index afd2dfa..67f2143 100644
--- a/backend/src/comment/comment.controller.ts
+++ b/backend/src/comment/comment.controller.ts
@@ -4,7 +4,13 @@ import { CreateCommentDto } from 'src/comment/dto/create-comment.dto';
 import { AuthGuard } from '@nestjs/passport';
 import { Request } from 'express';
 import { DeleteCommentDto } from 'src/comment/dto/delete-comment.dto';
-import { ApiBody, ApiCookieAuth, ApiOperation, ApiTags } from '@nestjs/swagger';
+import {
+  ApiBody,
+  ApiCookieAuth,
+  ApiOperation,
+  ApiResponse,
+  ApiTags,
+} from '@nestjs/swagger';
 
 @Controller('comment')
 @ApiTags('댓글 api')
@@ -15,6 +21,14 @@ export class CommentController {
   @ApiCookieAuth('accessToken')
   @Post()
   @ApiOperation({ summary: '아이템에 댓글을 입력합니다.' })
+  @ApiResponse({
+    status: 200,
+    description: '댓글이 성공적으로 입력되었습니다.',
+  })
+  @ApiResponse({
+    status: 404,
+    description: '아이템 또는 유저를 찾을 수 없습니다.',
+  })
   @ApiBody({ type: CreateCommentDto })
   async createComment(
     @Req() req: Request,
diff --git a/backend/src/game/game.entity.ts b/backend/src/game/game.entity.ts
index 13c24e0..c8b0c2e 100644
--- a/backend/src/game/game.entity.ts
+++ b/backend/src/game/game.entity.ts
@@ -1,5 +1,6 @@
 import { ApiProperty } from '@nestjs/swagger';
 import { Item } from 'src/item/item.entity';
+import { SelectedItem } from 'src/selected-item/selected-item.entity';
 import { User } from 'src/user/user.entity';
 import {
   Entity,
@@ -37,4 +38,11 @@ export class Game {
     type: () => [Item],
   })
   items: Item[];
+
+  @OneToMany(() => SelectedItem, (selectedItem) => selectedItem.game)
+  @ApiProperty({
+    description: '게임에서 선택된 아이템들',
+    type: () => [SelectedItem],
+  })
+  selectedItems: SelectedItem[];
 }
diff --git a/backend/src/item/item.entity.ts b/backend/src/item/item.entity.ts
index 15b799c..b67661e 100644
--- a/backend/src/item/item.entity.ts
+++ b/backend/src/item/item.entity.ts
@@ -1,6 +1,7 @@
 import { ApiProperty } from '@nestjs/swagger';
 import { Comment } from 'src/comment/comment.entity';
 import { Game } from 'src/game/game.entity';
+import { SelectedItem } from 'src/selected-item/selected-item.entity';
 import {
   Entity,
   PrimaryGeneratedColumn,
@@ -47,4 +48,11 @@ export class Item {
     example: 1,
   })
   selected_count: number;
+
+  @OneToMany(() => SelectedItem, (selectedItem) => selectedItem.item)
+  @ApiProperty({
+    description: '아이템이 선택된 기록들',
+    type: () => [SelectedItem],
+  })
+  selectedItems: SelectedItem[];
 }
diff --git a/backend/src/like/like.controller.ts b/backend/src/like/like.controller.ts
index 216bc30..a6ccafe 100644
--- a/backend/src/like/like.controller.ts
+++ b/backend/src/like/like.controller.ts
@@ -26,7 +26,7 @@ export class LikeController {
   @Post(':comment_id')
   @ApiCookieAuth('accessToken')
   @ApiOperation({ summary: '댓글 좋아요' })
-  @ApiResponse({ status: 201, description: '정상' })
+  @ApiResponse({ status: 200, description: '정상' })
   @ApiResponse({ status: 404, description: '유저 또는 댓글이 없습니다.' })
   @ApiResponse({
     status: 409,
diff --git a/backend/src/selected-item/selected-item.controller.ts b/backend/src/selected-item/selected-item.controller.ts
new file mode 100644
index 0000000..6cc8600
--- /dev/null
+++ b/backend/src/selected-item/selected-item.controller.ts
@@ -0,0 +1,21 @@
+import { Controller, Param, Post, Req, UseGuards } from '@nestjs/common';
+import { SelectedItemService } from './selected-item.service';
+import { AuthGuard } from '@nestjs/passport';
+import { Request } from 'express';
+
+@Controller('games/:gameId/items/:itemId/select')
+export class SelectedItemController {
+  constructor(private readonly selectedItemService: SelectedItemService) {}
+
+  @UseGuards(AuthGuard('jwt'))
+  @Post()
+  async selectOrToggleItem(
+    @Param('gameId') gameId: string,
+    @Param('itemId') itemId: string,
+    @Req() req: Request,
+  ): Promise<void> {
+    const kakaoId = req.user.kakaoId;
+
+    await this.selectedItemService.selectOrToggleItem(kakaoId, gameId, itemId);
+  }
+}
diff --git a/backend/src/selected-item/selected-item.entity.ts b/backend/src/selected-item/selected-item.entity.ts
new file mode 100644
index 0000000..599a3d8
--- /dev/null
+++ b/backend/src/selected-item/selected-item.entity.ts
@@ -0,0 +1,54 @@
+import { ApiProperty } from '@nestjs/swagger';
+import { User } from 'src/user/user.entity';
+import { Item } from 'src/item/item.entity';
+import { Game } from 'src/game/game.entity';
+import {
+  Entity,
+  PrimaryGeneratedColumn,
+  ManyToOne,
+  CreateDateColumn,
+  Unique,
+  JoinColumn,
+} from 'typeorm';
+
+@Entity()
+@Unique(['user', 'game']) // 특정 사용자가 같은 게임에서 한 번만 선택하도록 제한
+export class SelectedItem {
+  @PrimaryGeneratedColumn('uuid')
+  @ApiProperty({
+    description: '선택된 아이템 기록의 고유 식별자',
+    example: '12312-12312-12312-12312',
+  })
+  selected_item_id: string;
+
+  @ManyToOne(() => User, (user) => user.selectedItems, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'user_id' }) // 외래 키 이름을 'user_id'로 명시적으로 설정
+  @ApiProperty({
+    description: '아이템을 선택한 사용자',
+    type: () => User,
+  })
+  user: User;
+
+  @ManyToOne(() => Game, (game) => game.selectedItems, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'game_id' }) // 외래 키 이름을 'game_id'로 명시적으로 설정
+  @ApiProperty({
+    description: '선택이 이루어진 게임',
+    type: () => Game,
+  })
+  game: Game;
+
+  @ManyToOne(() => Item, (item) => item.selectedItems, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'item_id' }) // 외래 키 이름을 'item_id'로 명시적으로 설정
+  @ApiProperty({
+    description: '선택된 아이템',
+    type: () => Item,
+  })
+  item: Item;
+
+  @CreateDateColumn()
+  @ApiProperty({
+    description: '아이템이 선택된 날짜와 시간',
+    example: '2024-09-21T10:20:30Z',
+  })
+  selected_at: Date;
+}
diff --git a/backend/src/selected-item/selected-item.module.ts b/backend/src/selected-item/selected-item.module.ts
new file mode 100644
index 0000000..3a61c1f
--- /dev/null
+++ b/backend/src/selected-item/selected-item.module.ts
@@ -0,0 +1,15 @@
+import { Module } from '@nestjs/common';
+import { SelectedItemService } from './selected-item.service';
+import { SelectedItemController } from './selected-item.controller';
+import { TypeOrmModule } from '@nestjs/typeorm';
+import { Item } from 'src/item/item.entity';
+import { User } from 'src/user/user.entity';
+import { Game } from 'src/game/game.entity';
+import { SelectedItem } from 'src/selected-item/selected-item.entity';
+
+@Module({
+  imports: [TypeOrmModule.forFeature([Item, User, Game, SelectedItem])],
+  controllers: [SelectedItemController],
+  providers: [SelectedItemService],
+})
+export class SelectedItemModule {}
diff --git a/backend/src/selected-item/selected-item.service.ts b/backend/src/selected-item/selected-item.service.ts
new file mode 100644
index 0000000..755c256
--- /dev/null
+++ b/backend/src/selected-item/selected-item.service.ts
@@ -0,0 +1,119 @@
+import { Injectable } from '@nestjs/common';
+import { InjectRepository } from '@nestjs/typeorm';
+import { Repository, DataSource } from 'typeorm';
+import { SelectedItem } from './selected-item.entity';
+import { User } from 'src/user/user.entity';
+import { Item } from 'src/item/item.entity';
+import { Game } from 'src/game/game.entity';
+import { NotFoundException, ConflictException } from '@nestjs/common';
+
+@Injectable()
+export class SelectedItemService {
+  constructor(
+    @InjectRepository(SelectedItem)
+    private selectedItemRepository: Repository<SelectedItem>,
+    @InjectRepository(Item)
+    private itemRepository: Repository<Item>,
+    @InjectRepository(Game)
+    private gameRepository: Repository<Game>,
+    @InjectRepository(User)
+    private userRepository: Repository<User>,
+    private readonly dataSource: DataSource,
+  ) {}
+
+  async selectOrToggleItem(
+    user_id: string,
+    game_id: string,
+    item_id: string,
+  ): Promise<void> {
+    const queryRunner = this.dataSource.createQueryRunner();
+
+    await queryRunner.connect();
+    await queryRunner.startTransaction();
+
+    try {
+      const user = await this.userRepository.findOneBy({ user_id });
+      if (!user) {
+        throw new NotFoundException('User not found');
+      }
+
+      const game = await this.gameRepository.findOneBy({ game_id });
+      const item = await this.itemRepository.findOneBy({ item_id });
+      if (!game || !item) {
+        throw new NotFoundException('Game or item not found');
+      }
+
+      const existingSelection = await queryRunner.manager.findOne(
+        SelectedItem,
+        {
+          where: {
+            user: { user_id: user.user_id },
+            game: { game_id: game.game_id },
+          },
+          relations: ['item'],
+        },
+      );
+
+      if (existingSelection) {
+        if (existingSelection.item.item_id === item.item_id) {
+          // 동일한 아이템을 선택하면 취소 (삭제)
+          await queryRunner.manager.remove(existingSelection);
+          await this.updateItemSelectionCount(queryRunner, item, -1); // 선택 횟수 감소
+        } else {
+          // 다른 아이템을 선택하면 이전 선택을 취소하고 새로운 아이템 선택
+          await queryRunner.manager.remove(existingSelection);
+          await this.updateItemSelectionCount(
+            queryRunner,
+            existingSelection.item,
+            -1,
+          ); // 이전 아이템 선택 횟수 감소
+          await this.createNewSelection(queryRunner, user, game, item); // 새로운 선택
+        }
+      } else {
+        // 중복 확인
+        const duplicateCheck = await queryRunner.manager.findOne(SelectedItem, {
+          where: { user, game, item },
+        });
+        if (duplicateCheck) {
+          throw new ConflictException('Duplicate selection exists');
+        }
+        // 처음 선택하는 경우
+        await this.createNewSelection(queryRunner, user, game, item);
+      }
+
+      await queryRunner.commitTransaction();
+    } catch (error) {
+      await queryRunner.rollbackTransaction();
+      throw error;
+    } finally {
+      await queryRunner.release();
+    }
+  }
+
+  private async createNewSelection(
+    queryRunner: any,
+    user: User,
+    game: Game,
+    item: Item,
+  ): Promise<void> {
+    const newSelection = this.selectedItemRepository.create({
+      user,
+      game,
+      item,
+    });
+    await queryRunner.manager.save(newSelection);
+    await this.updateItemSelectionCount(queryRunner, item, 1); // 선택 횟수 증가
+  }
+
+  private async updateItemSelectionCount(
+    queryRunner: any,
+    item: Item,
+    countChange: number,
+  ): Promise<void> {
+    if (item.selected_count === undefined || item.selected_count === null) {
+      item.selected_count = 0; // 기본값 설정
+    }
+    item.selected_count += countChange;
+    await queryRunner.manager.save(item);
+  }
+}
diff --git a/backend/src/user/user.entity.ts b/backend/src/user/user.entity.ts
index c71d098..12b9b16 100644
--- a/backend/src/user/user.entity.ts
+++ b/backend/src/user/user.entity.ts
@@ -1,23 +1,52 @@
+import { ApiProperty } from '@nestjs/swagger';
 import { Comment } from 'src/comment/comment.entity';
 import { Game } from 'src/game/game.entity';
 import { Like } from 'src/like/like.entity';
+import { SelectedItem } from 'src/selected-item/selected-item.entity';
 import { Entity, Column, OneToMany, Unique, PrimaryColumn } from 'typeorm';
 
 @Entity()
 @Unique(['user_id'])
 export class User {
   @PrimaryColumn()
+  @ApiProperty({
+    description: '사용자의 고유 식별자',
+    example: '1234567890',
+  })
   user_id: string;
 
   @Column({ unique: true })
+  @ApiProperty({
+    description: '사용자의 닉네임',
+    example: 'username',
+  })
   username: string;
 
   @OneToMany(() => Game, (balanceGame) => balanceGame.user)
+  @ApiProperty({
+    description: '사용자가 만든 게임들',
+    type: () => [Game],
+  })
   games: Game[];
 
   @OneToMany(() => Comment, (comment) => comment.user)
+  @ApiProperty({
+    description: '사용자가 단 댓글들',
+    type: () => [Comment],
+  })
   comments: Comment[];
 
   @OneToMany(() => Like, (like) => like.user)
+  @ApiProperty({
+    description: '사용자가 누른 좋아요들',
+    type: () => [Like],
+  })
   likes: Like[];
+
+  @OneToMany(() => SelectedItem, (selectedItem) => selectedItem.user)
+  @ApiProperty({
+    description: '사용자가 선택한 아이템들',
+    type: () => [SelectedItem],
+  })
+  selectedItems: SelectedItem[];
 }