diff --git a/apps/backend/src/app.module.ts b/apps/backend/src/app.module.ts
index 390a0d1c5..d23aae40e 100644
--- a/apps/backend/src/app.module.ts
+++ b/apps/backend/src/app.module.ts
@@ -3,6 +3,7 @@ import { TypeOrmModule } from '@nestjs/typeorm';
 import { ConfigModule, ConfigService } from '@nestjs/config';
 import typeorm from './config/typeorm';
 import { CognitoModule } from './aws/cognito/cognito.module';
+import { RecommendationsModule } from './recommendations/recommendations.module';
 import { MatchesModule } from './matches/matches.module';
 import { CoordinatorsModule } from './coordinators/coordinators.module';
 import { VolunteersModule } from './volunteers/volunteers.module';
@@ -19,6 +20,7 @@ import { VolunteersModule } from './volunteers/volunteers.module';
         configService.getOrThrow('typeorm'),
     }),
     CognitoModule,
+    RecommendationsModule,
     MatchesModule,
     CoordinatorsModule,
     VolunteersModule,
diff --git a/apps/backend/src/recommendations/dto/create-recommendation.dto.ts b/apps/backend/src/recommendations/dto/create-recommendation.dto.ts
new file mode 100644
index 000000000..0976d2321
--- /dev/null
+++ b/apps/backend/src/recommendations/dto/create-recommendation.dto.ts
@@ -0,0 +1,11 @@
+import { IsInt, IsPositive } from 'class-validator';
+
+export class CreateRecommendationDTO {
+  @IsInt()
+  @IsPositive()
+  volunteerId!: number;
+
+  @IsInt()
+  @IsPositive()
+  chameleonAnimalId!: number;
+}
diff --git a/apps/backend/src/recommendations/recommendations.controller.spec.ts b/apps/backend/src/recommendations/recommendations.controller.spec.ts
index 748a2c3fc..5149a8e40 100644
--- a/apps/backend/src/recommendations/recommendations.controller.spec.ts
+++ b/apps/backend/src/recommendations/recommendations.controller.spec.ts
@@ -1,17 +1,35 @@
 import { Test, TestingModule } from '@nestjs/testing';
+import { NotFoundException } from '@nestjs/common';
 import { RecommendationsController } from './recommendations.controller';
 import { RecommendationsService } from './recommendations.service';
+import { Recommendation } from './recommendations.entity';
+import { CreateRecommendationDTO } from './dto/create-recommendation.dto';
+import { VolunteersService } from '../volunteers/volunteers.service';
 
 describe('RecommendationsController', () => {
   let controller: RecommendationsController;
+  let recommendationsService: { create: jest.Mock };
+  let volunteersService: { findActiveOrFail: jest.Mock };
+
+  const body = {
+    volunteerId: 7,
+    chameleonAnimalId: 42,
+  } as CreateRecommendationDTO;
 
   beforeEach(async () => {
+    recommendationsService = { create: jest.fn() };
+    volunteersService = { findActiveOrFail: jest.fn() };
+
     const module: TestingModule = await Test.createTestingModule({
       controllers: [RecommendationsController],
       providers: [
         {
           provide: RecommendationsService,
-          useValue: {},
+          useValue: recommendationsService,
+        },
+        {
+          provide: VolunteersService,
+          useValue: volunteersService,
         },
       ],
     }).compile();
@@ -24,4 +42,28 @@ describe('RecommendationsController', () => {
   it('should be defined', () => {
     expect(controller).toBeDefined();
   });
+
+  describe('createRecommendation', () => {
+    it('returns the created recommendation when the volunteer is active', async () => {
+      const recommendation = { ...body, isActive: true } as Recommendation;
+      volunteersService.findActiveOrFail.mockResolvedValue({});
+      recommendationsService.create.mockResolvedValue(recommendation);
+
+      const result = await controller.createRecommendation(body);
+
+      expect(result).toBe(recommendation);
+      expect(volunteersService.findActiveOrFail).toHaveBeenCalledWith(7);
+      expect(recommendationsService.create).toHaveBeenCalledWith(body);
+    });
+
+    it('does not create a recommendation when the volunteer does not exist or is not active', async () => {
+      const error = new NotFoundException();
+      volunteersService.findActiveOrFail.mockRejectedValue(error);
+
+      await expect(controller.createRecommendation(body)).rejects.toThrow(
+        error,
+      );
+      expect(recommendationsService.create).not.toHaveBeenCalled();
+    });
+  });
 });
diff --git a/apps/backend/src/recommendations/recommendations.controller.ts b/apps/backend/src/recommendations/recommendations.controller.ts
index ed58b1def..3ddf5ec42 100644
--- a/apps/backend/src/recommendations/recommendations.controller.ts
+++ b/apps/backend/src/recommendations/recommendations.controller.ts
@@ -1,7 +1,37 @@
-import { Controller } from '@nestjs/common';
+import { Body, Controller, HttpStatus, Post } from '@nestjs/common';
+import { ApiOperation, ApiResponse, ApiTags } from '@nestjs/swagger';
 import { RecommendationsService } from './recommendations.service';
+import { Recommendation } from './recommendations.entity';
+import { CreateRecommendationDTO } from './dto/create-recommendation.dto';
+import { VolunteersService } from '../volunteers/volunteers.service';
+import { validateId } from '../utils/validation.utils';
 
+@ApiTags('Recommendations')
+// @ApiBearerAuth()
 @Controller('recommendations')
 export class RecommendationsController {
-  constructor(private recommendationsService: RecommendationsService) {}
+  constructor(
+    private recommendationsService: RecommendationsService,
+    private volunteersService: VolunteersService,
+  ) {}
+
+  @Post()
+  @ApiOperation({
+    summary: 'Recommend a Chameleon Animal to an active Volunteer',
+  })
+  @ApiResponse({
+    status: HttpStatus.CREATED,
+    description: 'The created or reactivated recommendation',
+    type: Recommendation,
+  })
+  async createRecommendation(
+    @Body() body: CreateRecommendationDTO,
+  ): Promise<Recommendation> {
+    validateId(body.volunteerId, 'Volunteer');
+    validateId(body.chameleonAnimalId, 'Chameleon Animal');
+
+    await this.volunteersService.findActiveOrFail(body.volunteerId);
+
+    return this.recommendationsService.create(body);
+  }
 }
diff --git a/apps/backend/src/recommendations/recommendations.module.ts b/apps/backend/src/recommendations/recommendations.module.ts
index af7c536b8..3dd562311 100644
--- a/apps/backend/src/recommendations/recommendations.module.ts
+++ b/apps/backend/src/recommendations/recommendations.module.ts
@@ -3,9 +3,10 @@ import { TypeOrmModule } from '@nestjs/typeorm';
 import { Recommendation } from './recommendations.entity';
 import { RecommendationsController } from './recommendations.controller';
 import { RecommendationsService } from './recommendations.service';
+import { VolunteersModule } from '../volunteers/volunteers.module';
 
 @Module({
-  imports: [TypeOrmModule.forFeature([Recommendation])],
+  imports: [TypeOrmModule.forFeature([Recommendation]), VolunteersModule],
   controllers: [RecommendationsController],
   providers: [RecommendationsService],
   exports: [RecommendationsService],
diff --git a/apps/backend/src/recommendations/recommendations.service.spec.ts b/apps/backend/src/recommendations/recommendations.service.spec.ts
index 5424b2ecd..d60296250 100644
--- a/apps/backend/src/recommendations/recommendations.service.spec.ts
+++ b/apps/backend/src/recommendations/recommendations.service.spec.ts
@@ -5,14 +5,26 @@ import { Recommendation } from './recommendations.entity';
 
 describe('RecommendationsService', () => {
   let service: RecommendationsService;
+  let repo: { upsert: jest.Mock; findOneByOrFail: jest.Mock };
+
+  const saved = {
+    volunteerId: 7,
+    chameleonAnimalId: 42,
+    isActive: true,
+  } as Recommendation;
 
   beforeEach(async () => {
+    repo = {
+      upsert: jest.fn().mockResolvedValue({ identifiers: [] }),
+      findOneByOrFail: jest.fn().mockResolvedValue(saved),
+    };
+
     const module: TestingModule = await Test.createTestingModule({
       providers: [
         RecommendationsService,
         {
           provide: getRepositoryToken(Recommendation),
-          useValue: {},
+          useValue: repo,
         },
       ],
     }).compile();
@@ -23,4 +35,56 @@ describe('RecommendationsService', () => {
   it('should be defined', () => {
     expect(service).toBeDefined();
   });
+
+  describe('create', () => {
+    it('upserts the recommendation as active on the composite key', async () => {
+      await service.create({ volunteerId: 7, chameleonAnimalId: 42 });
+
+      expect(repo.upsert).toHaveBeenCalledWith(
+        { volunteerId: 7, chameleonAnimalId: 42, isActive: true },
+        ['volunteerId', 'chameleonAnimalId'],
+      );
+    });
+
+    it('reactivates an inactive recommendation for the same pair', async () => {
+      const result = await service.create({
+        volunteerId: 7,
+        chameleonAnimalId: 42,
+      });
+
+      expect(repo.upsert).toHaveBeenCalledWith(
+        expect.objectContaining({ isActive: true }),
+        ['volunteerId', 'chameleonAnimalId'],
+      );
+      expect(result.isActive).toBe(true);
+    });
+
+    it('returns the persisted recommendation', async () => {
+      const result = await service.create({
+        volunteerId: 7,
+        chameleonAnimalId: 42,
+      });
+
+      expect(result).toBe(saved);
+      expect(repo.findOneByOrFail).toHaveBeenCalledWith({
+        volunteerId: 7,
+        chameleonAnimalId: 42,
+      });
+    });
+
+    it('reads the row back only after the upsert has resolved', async () => {
+      const order: string[] = [];
+      repo.upsert.mockImplementation(async () => {
+        order.push('upsert');
+      });
+      repo.findOneByOrFail.mockImplementation(async () => {
+        order.push('read');
+        return saved;
+      });
+
+      await service.create({ volunteerId: 7, chameleonAnimalId: 42 });
+
+      expect(order).toEqual(['upsert', 'read']);
+    });
+  });
 });
diff --git a/apps/backend/src/recommendations/recommendations.service.ts b/apps/backend/src/recommendations/recommendations.service.ts
index 72688a007..7dfa3be98 100644
--- a/apps/backend/src/recommendations/recommendations.service.ts
+++ b/apps/backend/src/recommendations/recommendations.service.ts
@@ -2,6 +2,7 @@ import { Injectable } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
 import { Recommendation } from './recommendations.entity';
+import { CreateRecommendationDTO } from './dto/create-recommendation.dto';
 
 @Injectable()
 export class RecommendationsService {
@@ -9,4 +10,29 @@ export class RecommendationsService {
     @InjectRepository(Recommendation)
     private repo: Repository<Recommendation>,
   ) {}
+
+  /**
+   * Recommends a Chameleon Animal to a Volunteer.
+   *
+   * (volunteerId, chameleonAnimalId) is the primary key, so recommending the
+   * same animal again reactivates the existing row instead of duplicating it.
+   * This upserts rather than save()-ing so that two concurrent requests for
+   * the same pair can't race into a primary key violation. Does not check
+   * that the Volunteer exists or is active; callers are expected to.
+   *
+   * @param dto - The Volunteer and Chameleon Animal IDs to link.
+   * @returns The active recommendation as persisted.
+   * @throws {EntityNotFoundError} If the row can't be read back after the upsert.
+   */
+  async create({
+    volunteerId,
+    chameleonAnimalId,
+  }: CreateRecommendationDTO): Promise<Recommendation> {
+    await this.repo.upsert({ volunteerId, chameleonAnimalId, isActive: true }, [
+      'volunteerId',
+      'chameleonAnimalId',
+    ]);
+
+    return this.repo.findOneByOrFail({ volunteerId, chameleonAnimalId });
+  }
 }
diff --git a/apps/backend/src/utils/validation.utils.spec.ts b/apps/backend/src/utils/validation.utils.spec.ts
index 6b3908403..9ac7b4b8d 100644
--- a/apps/backend/src/utils/validation.utils.spec.ts
+++ b/apps/backend/src/utils/validation.utils.spec.ts
@@ -11,4 +11,16 @@ describe('validateId', () => {
       new BadRequestException('Invalid User ID'),
     );
   });
+
+  it('should throw BadRequestException for a non-integer ID', () => {
+    expect(() => validateId(1.5, 'User')).toThrow(
+      new BadRequestException('Invalid User ID'),
+    );
+  });
+
+  it('should throw BadRequestException for a missing ID', () => {
+    expect(() => validateId(undefined as unknown as number, 'User')).toThrow(
+      new BadRequestException('Invalid User ID'),
+    );
+  });
 });
diff --git a/apps/backend/src/utils/validation.utils.ts b/apps/backend/src/utils/validation.utils.ts
index 5c4f14a78..a02ac8d94 100644
--- a/apps/backend/src/utils/validation.utils.ts
+++ b/apps/backend/src/utils/validation.utils.ts
@@ -1,7 +1,7 @@
 import { BadRequestException } from '@nestjs/common';
 
 export function validateId(id: number, entityName: string): void {
-  if (!id || id < 1) {
+  if (!Number.isInteger(id) || id < 1) {
     throw new BadRequestException(`Invalid ${entityName} ID`);
   }
 }