diff --git a/addons/project/models/project.py b/addons/project/models/project.py
index 5cc110fbe31..a227c6a3bb3 100644
--- a/addons/project/models/project.py
+++ b/addons/project/models/project.py
@@ -1764,6 +1764,8 @@ class Task(models.Model):
                 vals['analytic_account_id'] = project.analytic_account_id.id
             if project.analytic_tag_ids:
                 vals['analytic_tag_ids'] = [Command.set(project.analytic_tag_ids.ids)]
+        else:
+            vals['user_ids'] = [Command.link(self.env.user.id)]
 
         return vals
 
@@ -1874,6 +1876,10 @@ class Task(models.Model):
             # user_ids change: update date_assign
             if vals.get('user_ids'):
                 vals['date_assign'] = fields.Datetime.now()
+                if not project_id:
+                    user_ids = self._fields['user_ids'].convert_to_cache(vals.get('user_ids', []), self)
+                    if self.env.user.id not in user_ids:
+                        vals['user_ids'] = [Command.set(list(user_ids) + [self.env.user.id])]
             # Stage change: Update date_end if folded stage and date_last_stage_update
             if vals.get('stage_id'):
                 vals.update(self.update_date_end(vals['stage_id']))
diff --git a/addons/project/tests/test_access_rights.py b/addons/project/tests/test_access_rights.py
index 8bab7f6f5bb..bf9dba4dd26 100644
--- a/addons/project/tests/test_access_rights.py
+++ b/addons/project/tests/test_access_rights.py
@@ -366,9 +366,37 @@ class TestAccessRightsPrivateTask(TestAccessRights):
         self.assertEqual(vals[0]['name'], private_task.name)
 
     @users('Project user')
-    def test_project_user_cannot_create_private_task_for_another_user(self):
-        with self.assertRaises(AccessError):
-            self.create_private_task('test private for another user', self.env.user, user_ids=[Command.set(self.user_projectuser.ids)])
+    def test_project_user_can_create_private_task_for_another_user(self):
+        self.create_private_task('Private task', user_ids=[Command.set(self.user_projectuser.ids)])
+
+    @users('Project user')
+    def test_project_current_user_is_added_in_private_task_assignees(self):
+        task_values = {'name': 'Private task'}
+        my_private_task = self.env['project.task'].create(task_values)
+        self.assertEqual(my_private_task.user_ids, self.env.user, 'When no assignee is set on a private task, the task should be assigned to the current user.')
+        user_projectuser_private_task = self.env['project.task'].create({**task_values, 'user_ids': [Command.set(self.user_projectuser.ids)]})
+        self.assertTrue(self.env.user in user_projectuser_private_task.user_ids, 'When creating a private task for another user, the current user should be added to the assignees.')
+
+    @users('Project user')
+    def test_project_current_user_is_added_in_task_assignees_when_project_id_is_set(self):
+        task_values = {'name': 'Private task', 'project_id': self.project_pigs.id, 'user_ids': [Command.set(self.user_projectuser.ids)]}
+        user_projectuser_task = self.env['project.task'].create(task_values)
+        self.assertFalse(self.env.user in user_projectuser_task.user_ids, "When creating a task that has a project for another user, the current user should not be added to the assignees.")
+
+    @users('Project user')
+    def test_project_current_user_is_set_as_assignee_in_task_when_project_id_is_set_with_no_assignees(self):
+        task = self.env['project.task'].create({'name': 'Private task', 'project_id': self.project_pigs.id})
+        self.assertEqual(task.user_ids, self.env.user, "When creating a task that has a project without assignees, the task will be assigned to the current user if no default_project_id is provided in the context (which is handled in _default_personal_stage_type_id).")
+
+    @users('Project user')
+    def test_project_current_user_is_not_added_in_private_task_assignees_when_default_project_id_is_in_the_context(self):
+        task_values = {'name': 'Private task'}
+        context = {'default_project_id': self.project_pigs.id}
+        ProjectTask_with_default_project_id = self.env['project.task'].with_context(context)
+        task = ProjectTask_with_default_project_id.create(task_values)
+        self.assertNotEqual(task.user_ids, self.env.user, "When creating a task without assignees and providing default_project_id in the context, the task should not be assigned to the current user.")
+        user_projectuser_task = ProjectTask_with_default_project_id.create({**task_values, 'user_ids': [Command.set(self.user_projectuser.ids)]})
+        self.assertFalse(self.env.user in user_projectuser_task.user_ids, "When creating a task for another user and providing default_project_id in the context, the current user should not be added to the assignees.")
 
     @users('Project user')
     def test_project_user_cannot_write_private_task_of_another_user(self):