diff --git a/ApiCore-Backend/src/app.module.ts b/ApiCore-Backend/src/app.module.ts
index f08d1c9..eb2855a 100644
--- a/ApiCore-Backend/src/app.module.ts
+++ b/ApiCore-Backend/src/app.module.ts
@@ -12,6 +12,7 @@ import { QueensModule } from './queens/queens.module';
 import { InspectionsModule } from './inspections/inspections.module';
 import { TasksModule } from './tasks/tasks.module';
 import { VarroaModule } from './varroa/varroa.module';
+import { TreatmentsModule } from './treatments/treatments.module';
 import { JwtAuthGuard } from './auth/guards/jwt-auth.guard';
 import { RolesGuard } from './auth/guards/roles.guard';
 
@@ -29,6 +30,7 @@ import { RolesGuard } from './auth/guards/roles.guard';
     InspectionsModule,
     TasksModule,
     VarroaModule,
+    TreatmentsModule,
   ],
   controllers: [],
   providers: [
diff --git a/ApiCore-Backend/src/treatments/colony-treatments.controller.ts b/ApiCore-Backend/src/treatments/colony-treatments.controller.ts
new file mode 100644
index 0000000..c881dac
--- /dev/null
+++ b/ApiCore-Backend/src/treatments/colony-treatments.controller.ts
@@ -0,0 +1,15 @@
+import { Controller, Get, Param } from '@nestjs/common';
+import { ApiBearerAuth, ApiTags } from '@nestjs/swagger';
+import { TreatmentsService } from './treatments.service';
+
+@ApiTags('treatments')
+@ApiBearerAuth()
+@Controller('colonies')
+export class ColonyTreatmentsController {
+  constructor(private readonly treatmentsService: TreatmentsService) {}
+
+  @Get(':id/treatments')
+  findByColony(@Param('id') id: string) {
+    return this.treatmentsService.findByColony(id);
+  }
+}
diff --git a/ApiCore-Backend/src/treatments/dto/create-treatment.dto.ts b/ApiCore-Backend/src/treatments/dto/create-treatment.dto.ts
new file mode 100644
index 0000000..d2ff58f
--- /dev/null
+++ b/ApiCore-Backend/src/treatments/dto/create-treatment.dto.ts
@@ -0,0 +1,56 @@
+import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
+import { IsDateString, IsOptional, IsString } from 'class-validator';
+
+export class CreateTreatmentDto {
+  @ApiProperty()
+  @IsString()
+  colonyId!: string;
+
+  @ApiProperty()
+  @IsDateString()
+  date!: string;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsDateString()
+  startDate?: string;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsDateString()
+  endDate?: string;
+
+  @ApiProperty()
+  @IsString()
+  product!: string;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsString()
+  activeIngredient?: string;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsString()
+  amount?: string;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsString()
+  method?: string;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsString()
+  reason?: string;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsString()
+  batchNumber?: string;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsString()
+  notes?: string;
+}
diff --git a/ApiCore-Backend/src/treatments/treatments.controller.ts b/ApiCore-Backend/src/treatments/treatments.controller.ts
new file mode 100644
index 0000000..e9160e3
--- /dev/null
+++ b/ApiCore-Backend/src/treatments/treatments.controller.ts
@@ -0,0 +1,34 @@
+import { Body, Controller, Get, Param, Post } from '@nestjs/common';
+import { ApiBearerAuth, ApiTags } from '@nestjs/swagger';
+import { Role } from '../../generated/prisma';
+import { Roles } from '../auth/decorators/roles.decorator';
+import { CurrentUser } from '../auth/decorators/current-user.decorator';
+import type { AuthenticatedUser } from '../auth/types/authenticated-user';
+import { CreateTreatmentDto } from './dto/create-treatment.dto';
+import { TreatmentsService } from './treatments.service';
+
+@ApiTags('treatments')
+@ApiBearerAuth()
+@Controller('treatments')
+export class TreatmentsController {
+  constructor(private readonly treatmentsService: TreatmentsService) {}
+
+  @Get()
+  findAll() {
+    return this.treatmentsService.findAll();
+  }
+
+  @Get(':id')
+  findOne(@Param('id') id: string) {
+    return this.treatmentsService.findById(id);
+  }
+
+  @Roles(Role.ADMIN, Role.BEEKEEPER)
+  @Post()
+  create(
+    @Body() dto: CreateTreatmentDto,
+    @CurrentUser() actor: AuthenticatedUser,
+  ) {
+    return this.treatmentsService.create(dto, actor.id);
+  }
+}
diff --git a/ApiCore-Backend/src/treatments/treatments.module.ts b/ApiCore-Backend/src/treatments/treatments.module.ts
new file mode 100644
index 0000000..53b63d1
--- /dev/null
+++ b/ApiCore-Backend/src/treatments/treatments.module.ts
@@ -0,0 +1,11 @@
+import { Module } from '@nestjs/common';
+import { TreatmentsController } from './treatments.controller';
+import { ColonyTreatmentsController } from './colony-treatments.controller';
+import { TreatmentsService } from './treatments.service';
+
+@Module({
+  controllers: [TreatmentsController, ColonyTreatmentsController],
+  providers: [TreatmentsService],
+  exports: [TreatmentsService],
+})
+export class TreatmentsModule {}
diff --git a/ApiCore-Backend/src/treatments/treatments.service.spec.ts b/ApiCore-Backend/src/treatments/treatments.service.spec.ts
new file mode 100644
index 0000000..b8c8717
--- /dev/null
+++ b/ApiCore-Backend/src/treatments/treatments.service.spec.ts
@@ -0,0 +1,72 @@
+import { NotFoundException } from '@nestjs/common';
+import { TreatmentsService } from './treatments.service';
+import { PrismaService } from '../prisma/prisma.service';
+import { AuditLogService } from '../audit/audit-log.service';
+
+describe('TreatmentsService', () => {
+  let service: TreatmentsService;
+  let prisma: {
+    treatment: {
+      findMany: jest.Mock;
+      findUnique: jest.Mock;
+      create: jest.Mock;
+    };
+  };
+  let auditLog: { record: jest.Mock };
+
+  const treatment = {
+    id: 'treatment-1',
+    colonyId: 'colony-1',
+    date: new Date(),
+  };
+
+  beforeEach(() => {
+    prisma = {
+      treatment: {
+        findMany: jest.fn(),
+        findUnique: jest.fn(),
+        create: jest.fn(),
+      },
+    };
+    auditLog = { record: jest.fn() };
+    service = new TreatmentsService(
+      prisma as unknown as PrismaService,
+      auditLog as unknown as AuditLogService,
+    );
+  });
+
+  it('findById throws NotFoundException when missing', async () => {
+    prisma.treatment.findUnique.mockResolvedValue(null);
+    await expect(service.findById('missing')).rejects.toBeInstanceOf(
+      NotFoundException,
+    );
+  });
+
+  it('create stores the acting user and product', async () => {
+    prisma.treatment.create.mockResolvedValue(treatment);
+
+    await service.create(
+      { colonyId: 'colony-1', date: '2026-01-01', product: 'Ameisensäure' },
+      'user-1',
+    );
+
+    const [[createArg]] = prisma.treatment.create.mock.calls as [
+      [{ data: { colonyId: string; userId: string; product: string } }],
+    ];
+    expect(createArg.data.colonyId).toBe('colony-1');
+    expect(createArg.data.userId).toBe('user-1');
+    expect(createArg.data.product).toBe('Ameisensäure');
+  });
+
+  it('findByColony orders results chronologically', async () => {
+    prisma.treatment.findMany.mockResolvedValue([treatment]);
+
+    await service.findByColony('colony-1');
+
+    const [[queryArg]] = prisma.treatment.findMany.mock.calls as [
+      [{ where: { colonyId: string }; orderBy: { date: string } }],
+    ];
+    expect(queryArg.where.colonyId).toBe('colony-1');
+    expect(queryArg.orderBy.date).toBe('asc');
+  });
+});
diff --git a/ApiCore-Backend/src/treatments/treatments.service.ts b/ApiCore-Backend/src/treatments/treatments.service.ts
new file mode 100644
index 0000000..30286f1
--- /dev/null
+++ b/ApiCore-Backend/src/treatments/treatments.service.ts
@@ -0,0 +1,55 @@
+import { Injectable, NotFoundException } from '@nestjs/common';
+import { PrismaService } from '../prisma/prisma.service';
+import { AuditLogService } from '../audit/audit-log.service';
+import { Treatment } from '../../generated/prisma';
+import { CreateTreatmentDto } from './dto/create-treatment.dto';
+
+@Injectable()
+export class TreatmentsService {
+  constructor(
+    private readonly prisma: PrismaService,
+    private readonly auditLog: AuditLogService,
+  ) {}
+
+  async findAll(): Promise<Treatment[]> {
+    return this.prisma.treatment.findMany({ orderBy: { date: 'desc' } });
+  }
+
+  async findById(id: string): Promise<Treatment> {
+    const treatment = await this.prisma.treatment.findUnique({ where: { id } });
+    if (!treatment) {
+      throw new NotFoundException('Treatment not found');
+    }
+    return treatment;
+  }
+
+  async findByColony(colonyId: string): Promise<Treatment[]> {
+    return this.prisma.treatment.findMany({
+      where: { colonyId },
+      orderBy: { date: 'asc' },
+    });
+  }
+
+  async create(
+    dto: CreateTreatmentDto,
+    actingUserId: string,
+  ): Promise<Treatment> {
+    const treatment = await this.prisma.treatment.create({
+      data: {
+        ...dto,
+        date: new Date(dto.date),
+        startDate: dto.startDate ? new Date(dto.startDate) : undefined,
+        endDate: dto.endDate ? new Date(dto.endDate) : undefined,
+        userId: actingUserId,
+      },
+    });
+    await this.auditLog.record({
+      entityType: 'Treatment',
+      entityId: treatment.id,
+      action: 'CREATE',
+      userId: actingUserId,
+      afterData: treatment,
+    });
+    return treatment;
+  }
+}
diff --git a/ApiCore-Backend/test/treatments.e2e-spec.ts b/ApiCore-Backend/test/treatments.e2e-spec.ts
new file mode 100644
index 0000000..c4e8cd9
--- /dev/null
+++ b/ApiCore-Backend/test/treatments.e2e-spec.ts
@@ -0,0 +1,114 @@
+import { INestApplication } from '@nestjs/common';
+import * as bcrypt from 'bcryptjs';
+import request from 'supertest';
+import { App } from 'supertest/types';
+import { PrismaService } from '../src/prisma/prisma.service';
+import { createTestApp } from './utils/create-test-app';
+import { login } from './utils/api';
+
+interface TreatmentBody {
+  id: string;
+  colonyId: string;
+}
+
+describe('Treatments (e2e)', () => {
+  let app: INestApplication<App>;
+  let prisma: PrismaService;
+  const beekeeperEmail = `treatments-e2e-beekeeper-${Date.now()}@example.com`;
+  const staffEmail = `treatments-e2e-staff-${Date.now()}@example.com`;
+  const password = 'SuperSecret123!';
+  let beekeeperId: string;
+  let staffId: string;
+  let beekeeperToken: string;
+  let staffToken: string;
+  let apiaryId: string;
+  let colonyId: string;
+  let treatmentId: string;
+
+  beforeAll(async () => {
+    app = await createTestApp();
+    prisma = app.get(PrismaService);
+
+    const passwordHash = await bcrypt.hash(password, 12);
+    const beekeeper = await prisma.user.create({
+      data: {
+        email: beekeeperEmail,
+        passwordHash,
+        name: 'Beekeeper',
+        role: 'BEEKEEPER',
+      },
+    });
+    beekeeperId = beekeeper.id;
+    const staff = await prisma.user.create({
+      data: { email: staffEmail, passwordHash, name: 'Staff', role: 'STAFF' },
+    });
+    staffId = staff.id;
+    beekeeperToken = (await login(app, beekeeperEmail, password)).accessToken;
+    staffToken = (await login(app, staffEmail, password)).accessToken;
+
+    const apiary = await prisma.apiary.create({
+      data: { name: `Stand ${Date.now()}` },
+    });
+    apiaryId = apiary.id;
+    const colony = await prisma.colony.create({
+      data: {
+        code: `V-${Date.now()}`,
+        apiaryId,
+        colonyType: 'PRODUCTION_COLONY',
+      },
+    });
+    colonyId = colony.id;
+  });
+
+  afterAll(async () => {
+    await prisma.treatment.deleteMany({ where: { colonyId } });
+    await prisma.colony.deleteMany({ where: { id: colonyId } });
+    await prisma.apiary.deleteMany({ where: { id: apiaryId } });
+    await prisma.refreshToken.deleteMany({
+      where: { userId: { in: [beekeeperId, staffId] } },
+    });
+    await prisma.auditLog.deleteMany({
+      where: { userId: { in: [beekeeperId, staffId] } },
+    });
+    await prisma.user.deleteMany({
+      where: { id: { in: [beekeeperId, staffId] } },
+    });
+    await app.close();
+  });
+
+  it('rejects create for a STAFF user', () => {
+    return request(app.getHttpServer())
+      .post('/api/v1/treatments')
+      .set('Authorization', `Bearer ${staffToken}`)
+      .send({
+        colonyId,
+        date: new Date().toISOString(),
+        product: 'Ameisensäure',
+      })
+      .expect(403);
+  });
+
+  it('lets a BEEKEEPER user record a treatment', async () => {
+    const response = await request(app.getHttpServer())
+      .post('/api/v1/treatments')
+      .set('Authorization', `Bearer ${beekeeperToken}`)
+      .send({
+        colonyId,
+        date: new Date().toISOString(),
+        product: 'Ameisensäure',
+        amount: '15 ml',
+      })
+      .expect(201);
+    treatmentId = (response.body as TreatmentBody).id;
+    expect(treatmentId).toEqual(expect.any(String));
+  });
+
+  it('lists treatments for the colony', async () => {
+    const response = await request(app.getHttpServer())
+      .get(`/api/v1/colonies/${colonyId}/treatments`)
+      .set('Authorization', `Bearer ${staffToken}`)
+      .expect(200);
+    const treatments = response.body as TreatmentBody[];
+    expect(treatments.some((entry) => entry.id === treatmentId)).toBe(true);
+  });
+});
diff --git a/TASKS.md b/TASKS.md
index f2bb3cb..7a063e4 100644
--- a/TASKS.md
+++ b/TASKS.md
@@ -74,7 +74,7 @@ Abgeleitet aus [`docs/lastenheft.md`](docs/lastenheft.md) Abschnitt 26. Reihenfo
 - Backend: `TreatmentsModule`
 - Endpunkte: `GET/POST /api/v1/treatments`, `GET /api/v1/colonies/:id/treatments`
 - Frontend: `/treatments/new`, `/colonies/[id]` Tab "Behandlungen"
-- [ ] Backend-Modul fertig, getestet, grün, committet
+- [x] Backend-Modul fertig, getestet, grün, committet
 - [ ] Frontend-Views fertig, getestet, grün, committet
 
 ### 9. Fütterungen