diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDao.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDao.java
index 70da2a754..b55cb8c1e 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDao.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDao.java
@@ -1,12 +1,28 @@
 package org.navalplanner.business.resources.daos;
 
 import org.navalplanner.business.common.daos.IGenericDao;
+import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
 import org.navalplanner.business.resources.entities.Worker;
 
 /**
  * DAO interface for the <code>Worker</code> entity.
  *
  * @author Fernando Bellas Permuy <fbellas@udc.es>
+ * @author Manuel Rego Casasnovas <mrego@igalia.com>
  *
  */
-public interface IWorkerDao extends IGenericDao<Worker, Long> {}
+public interface IWorkerDao extends IGenericDao<Worker, Long> {
+
+    /**
+     * Finds a {@link Worker} with the NIF param that should be unique.
+     *
+     * @param nif
+     *            The NIF to search the {@link Worker}
+     * @return The {@link Worker} with this NIF
+     * @throws InstanceNotFoundException
+     *             If there're more than one {@link Worker} with this NIF or
+     *             there isn't any {@link Worker} with this NIF
+     */
+    Worker findUniqueByNif(String nif) throws InstanceNotFoundException;
+
+}
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/impl/WorkerDaoHibernate.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/impl/WorkerDaoHibernate.java
index 6831dfeb4..4d5c05a5e 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/impl/WorkerDaoHibernate.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/impl/WorkerDaoHibernate.java
@@ -1,6 +1,11 @@
 package org.navalplanner.business.resources.daos.impl;
 
+import java.util.List;
+
+import org.hibernate.Criteria;
+import org.hibernate.criterion.Restrictions;
 import org.navalplanner.business.common.daos.impl.GenericDaoHibernate;
+import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
 import org.navalplanner.business.resources.daos.IWorkerDao;
 import org.navalplanner.business.resources.entities.Worker;
 import org.springframework.beans.factory.config.BeanDefinition;
@@ -11,9 +16,26 @@ import org.springframework.stereotype.Repository;
  * Hibernate DAO for the <code>Worker</code> entity.
  *
  * @author Fernando Bellas Permuy <fbellas@udc.es>
+ * @author Manuel Rego Casasnovas <mrego@igalia.com>
  *
  */
 @Repository
 @Scope(BeanDefinition.SCOPE_SINGLETON)
 public class WorkerDaoHibernate extends GenericDaoHibernate<Worker, Long>
-    implements IWorkerDao {}
+    implements IWorkerDao {
+
+    @Override
+    public Worker findUniqueByNif(String nif) throws InstanceNotFoundException {
+        Criteria criteria = getSession().createCriteria(Worker.class);
+        criteria.add(Restrictions.eq("nif", nif).ignoreCase());
+
+        List<Worker> list = criteria.list();
+
+        if (list.size() != 1) {
+            throw new InstanceNotFoundException(nif, Worker.class.getName());
+        }
+
+        return list.get(0);
+    }
+
+}