diff --git a/src/main/java/de/hmmh/pmt/ApiController.java b/src/main/java/de/hmmh/pmt/ApiController.java
index c20b9f4..4d0ca78 100644
--- a/src/main/java/de/hmmh/pmt/ApiController.java
+++ b/src/main/java/de/hmmh/pmt/ApiController.java
@@ -1,15 +1,14 @@
 package de.hmmh.pmt;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
+import de.hmmh.pmt.db.Allocation;
 import de.hmmh.pmt.db.AllocationRepository;
-import de.hmmh.pmt.employee.ApiClientFactory;
 import de.hmmh.pmt.db.Project;
 import de.hmmh.pmt.db.ProjectRepository;
-import de.hmmh.pmt.dtos.CreateProjectDTO;
-import de.hmmh.pmt.dtos.CreatedProjectDTO;
-import de.hmmh.pmt.dtos.GetAllProjectsDTO;
-import de.hmmh.pmt.dtos.ProjectInfo;
+import de.hmmh.pmt.dtos.*;
 import de.hmmh.pmt.employee.ApiClientFactory;
+import de.hmmh.pmt.employee.dtos.EmployeeResponseDTO;
+import de.hmmh.pmt.employee.dtos.QualificationGetDTO;
 import de.hmmh.pmt.oas.DefaultApi;
 import de.hmmh.pmt.util.Mapper;
 import jakarta.servlet.http.HttpServletRequest;
@@ -21,6 +20,7 @@ import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.client.HttpClientErrorException;
 import org.springframework.web.client.RestClientException;
 
+import java.util.List;
 import java.util.Optional;
 
 @Controller
@@ -96,4 +96,46 @@ public class ApiController implements DefaultApi {
         CreatedProjectDTO response = mapper.map(project);
         return new ResponseEntity<>(response, HttpStatus.CREATED);
     }
-}
+
+    @Override
+    public ResponseEntity<Void> addEmployee(Long id, AddEmployeeDTO body) {
+
+        Optional<Project> optionalProject = projectRepository.findById(id);
+        if (optionalProject.isEmpty()) {
+            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
+        }
+        try {
+            EmployeeResponseDTO employee = apiClientFactory.getEmployeeApi().findById(body.getEmployeeId());
+            List<QualificationGetDTO> qualifications = employee.getSkillSet();
+            if (!hasQualification(qualifications, body.getQualificationId())) {
+                return new ResponseEntity<>(HttpStatus.NOT_ACCEPTABLE);
+            }
+
+            Project project = optionalProject.get();
+            if (allocationRepository.hasOverlappingAllocation(employee.getId(), project.getStart(), project.getPlannedEnd())) {
+                return new ResponseEntity<>(HttpStatus.CONFLICT);
+            }
+            Allocation allocation = new Allocation();
+            allocation.setEmployeeId(employee.getId());
+            allocation.setRole(body.getQualificationId());
+            allocation.setProjectId(project.getId());
+            allocationRepository.save(allocation);
+
+            return new ResponseEntity<>(HttpStatus.NO_CONTENT);
+
+        } catch (HttpClientErrorException exception) {
+            return new ResponseEntity<>(exception.getStatusCode().equals(HttpStatus.NOT_FOUND)
+                    ? HttpStatus.NOT_FOUND
+                    : HttpStatus.INTERNAL_SERVER_ERROR);
+        }
+    }
+
+    private boolean hasQualification(List<QualificationGetDTO> qualifications, Long neededQualificationId) {
+        for (QualificationGetDTO qualification : qualifications) {
+            if (qualification.getId().equals(neededQualificationId)) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/de/hmmh/pmt/db/AllocationRepository.java b/src/main/java/de/hmmh/pmt/db/AllocationRepository.java
index 387b20f..8321dcd 100644
--- a/src/main/java/de/hmmh/pmt/db/AllocationRepository.java
+++ b/src/main/java/de/hmmh/pmt/db/AllocationRepository.java
@@ -1,7 +1,15 @@
 package de.hmmh.pmt.db;
 
+import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.CrudRepository;
 
+import java.time.LocalDateTime;
+
 public interface AllocationRepository extends CrudRepository<Allocation, AllocationId> {
-    
+
+    @Query("SELECT COUNT(a) > 0 FROM Allocation a " +
+            "WHERE a.employeeId = :employeeId " +
+            "AND a.project.start <= :endDate " +
+            "AND a.project.plannedEnd >= :startDate")
+    boolean hasOverlappingAllocation(Long employeeId, LocalDateTime startDate, LocalDateTime endDate);
 }