diff --git a/src/EventListener/TaskNotificationListener.php b/src/EventListener/TaskNotificationListener.php
index 26455d1..1795184 100644
--- a/src/EventListener/TaskNotificationListener.php
+++ b/src/EventListener/TaskNotificationListener.php
@@ -57,6 +57,22 @@ final class TaskNotificationListener
                 $this->pending[] = ['user' => $new, 'type' => 'task_assigned', 'task' => $entity];
             }
         }
+
+        // Ajout de collaborateur(s) (tâche nouvelle ou existante).
+        foreach ($uow->getScheduledCollectionUpdates() as $collection) {
+            $owner = $collection->getOwner();
+            if (!$owner instanceof Task) {
+                continue;
+            }
+            if ('collaborators' !== $collection->getMapping()->fieldName) {
+                continue;
+            }
+            foreach ($collection->getInsertDiff() as $user) {
+                if ($user instanceof User && $user !== $actor) {
+                    $this->pending[] = ['user' => $user, 'type' => 'task_collaborator_added', 'task' => $owner];
+                }
+            }
+        }
     }
 
     public function postFlush(PostFlushEventArgs $args): void
diff --git a/tests/Functional/EventListener/TaskNotificationListenerTest.php b/tests/Functional/EventListener/TaskNotificationListenerTest.php
index 57ad4e0..158fd17 100644
--- a/tests/Functional/EventListener/TaskNotificationListenerTest.php
+++ b/tests/Functional/EventListener/TaskNotificationListenerTest.php
@@ -115,6 +115,36 @@ class TaskNotificationListenerTest extends KernelTestCase
         self::assertCount(0, $this->notifications->findBy(['user' => $this->alice]));
     }
 
+    public function testAddingCollaboratorCreatesNotification(): void
+    {
+        $this->loginAs($this->actor);
+
+        $task = $this->makeTask();
+        $this->em->persist($task);
+        $this->em->flush();
+
+        $task->addCollaborator($this->alice);
+        $this->em->flush();
+
+        $rows = $this->notifications->findBy(['user' => $this->alice]);
+        self::assertCount(1, $rows);
+        self::assertSame('task_collaborator_added', $rows[0]->getType());
+    }
+
+    public function testAddingSelfAsCollaboratorCreatesNoNotification(): void
+    {
+        $this->loginAs($this->actor);
+
+        $task = $this->makeTask();
+        $this->em->persist($task);
+        $this->em->flush();
+
+        $task->addCollaborator($this->actor);
+        $this->em->flush();
+
+        self::assertCount(0, $this->notifications->findBy(['user' => $this->actor]));
+    }
+
     private function makeUser(string $prefix): User
     {
         $user = new User();