diff --git a/dspace-api/src/main/resources/Messages.properties b/dspace-api/src/main/resources/Messages.properties
index 0583fb493c..b537819c06 100644
--- a/dspace-api/src/main/resources/Messages.properties
+++ b/dspace-api/src/main/resources/Messages.properties
@@ -119,3 +119,4 @@ org.dspace.app.rest.exception.RESTEmptyWorkflowGroupException.message = Refused
     workflow group {1}. Delete the tasks and group first if you want to remove this user.
 org.dspace.app.rest.exception.EPersonNameNotProvidedException.message = The eperson.firstname and eperson.lastname values need to be filled in
 org.dspace.app.rest.exception.GroupNameNotProvidedException.message = Cannot create group, no group name is provided
+org.dspace.app.rest.exception.GroupHasPendingWorkflowTasksException.message = Cannot delete group, the associated workflow role still has pending tasks
diff --git a/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/DSpaceApiExceptionControllerAdvice.java b/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/DSpaceApiExceptionControllerAdvice.java
index d57e637047..8e7fdc23e4 100644
--- a/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/DSpaceApiExceptionControllerAdvice.java
+++ b/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/DSpaceApiExceptionControllerAdvice.java
@@ -133,6 +133,7 @@ public class DSpaceApiExceptionControllerAdvice extends ResponseEntityExceptionH
         RESTEmptyWorkflowGroupException.class,
         EPersonNameNotProvidedException.class,
         GroupNameNotProvidedException.class,
+        GroupHasPendingWorkflowTasksException.class,
     })
     protected void handleCustomUnprocessableEntityException(HttpServletRequest request, HttpServletResponse response,
                                                             TranslatableException ex) throws IOException {
diff --git a/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/GroupHasPendingWorkflowTasksException.java b/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/GroupHasPendingWorkflowTasksException.java
new file mode 100644
index 0000000000..cd50ce19bf
--- /dev/null
+++ b/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/GroupHasPendingWorkflowTasksException.java
@@ -0,0 +1,36 @@
+/**
+ * The contents of this file are subject to the license and copyright
+ * detailed in the LICENSE and NOTICE files at the root of the source
+ * tree and available online at
+ *
+ * http://www.dspace.org/license/
+ */
+
+package org.dspace.app.rest.exception;
+
+import org.dspace.core.I18nUtil;
+
+/**
+ * <p>Extend {@link UnprocessableEntityException} to provide a specific error message
+ * in the REST response. The error message is added to the response in
+ * {@link DSpaceApiExceptionControllerAdvice#handleCustomUnprocessableEntityException},
+ * hence it should not contain sensitive or security-compromising info.</p>
+ *
+ */
+public class GroupHasPendingWorkflowTasksException
+        extends UnprocessableEntityException implements TranslatableException {
+    public static final String MESSAGE_KEY =
+        "org.dspace.app.rest.exception.GroupHasPendingTasksException.message";
+
+    public GroupHasPendingWorkflowTasksException() {
+        super(I18nUtil.getMessage(MESSAGE_KEY));
+    }
+
+    public GroupHasPendingWorkflowTasksException(Throwable cause) {
+        super(I18nUtil.getMessage(MESSAGE_KEY), cause);
+    }
+
+    public String getMessageKey() {
+        return MESSAGE_KEY;
+    }
+}
diff --git a/dspace-server-webapp/src/main/java/org/dspace/app/rest/repository/CollectionRestRepository.java b/dspace-server-webapp/src/main/java/org/dspace/app/rest/repository/CollectionRestRepository.java
index 4a769709d3..ba3163a444 100644
--- a/dspace-server-webapp/src/main/java/org/dspace/app/rest/repository/CollectionRestRepository.java
+++ b/dspace-server-webapp/src/main/java/org/dspace/app/rest/repository/CollectionRestRepository.java
@@ -24,6 +24,7 @@ import org.apache.logging.log4j.Logger;
 import org.dspace.app.rest.Parameter;
 import org.dspace.app.rest.SearchRestMethod;
 import org.dspace.app.rest.exception.DSpaceBadRequestException;
+import org.dspace.app.rest.exception.GroupHasPendingWorkflowTasksException;
 import org.dspace.app.rest.exception.RepositoryMethodNotImplementedException;
 import org.dspace.app.rest.exception.UnprocessableEntityException;
 import org.dspace.app.rest.model.BitstreamRest;
@@ -695,8 +696,8 @@ public class CollectionRestRepository extends DSpaceObjectRestRepository<Collect
         throws SQLException, WorkflowConfigurationException, AuthorizeException, WorkflowException, IOException {
         Group group = workflowService.getWorkflowRoleGroup(context, collection, workflowRole, null);
         if (!poolTaskService.findByGroup(context, group).isEmpty()) {
-            throw new UnprocessableEntityException("The Group that was attempted to be deleted " +
-                                                       "still has Pooltasks open");
+            // todo: also handle claimed tasks that would become associated with this group once returned to the pool
+            throw new GroupHasPendingWorkflowTasksException();
         }
         if (group == null) {
             throw new ResourceNotFoundException("The requested Group was not found");
diff --git a/dspace-server-webapp/src/test/resources/Messages_pl.properties b/dspace-server-webapp/src/test/resources/Messages_pl.properties
index 9f2db2e0da..3513cdd316 100644
--- a/dspace-server-webapp/src/test/resources/Messages_pl.properties
+++ b/dspace-server-webapp/src/test/resources/Messages_pl.properties
@@ -11,3 +11,4 @@ org.dspace.app.rest.exception.RESTEmptyWorkflowGroupException.message = [PL] Ref
     workflow group {1}. Delete the tasks and group first if you want to remove this user.
 org.dspace.app.rest.exception.EPersonNameNotProvidedException.message = [PL] The eperson.firstname and eperson.lastname values need to be filled in
 org.dspace.app.rest.exception.GroupNameNotProvidedException.message = [PL] Cannot create group, no group name is provided
+org.dspace.app.rest.exception.GroupHasPendingWorkflowTasksException.message = [PL] Cannot delete group, the associated workflow role still has pending tasks