diff --git a/task-sdk/src/airflow/sdk/bases/operator.py b/task-sdk/src/airflow/sdk/bases/operator.py
index c430f38982348..6f0078eef535c 100644
--- a/task-sdk/src/airflow/sdk/bases/operator.py
+++ b/task-sdk/src/airflow/sdk/bases/operator.py
@@ -1022,9 +1022,13 @@ def __init__(
     ):
         # Note: Metaclass handles passing in the DAG/TaskGroup from active context manager, if any
 
-        self.task_id = task_group.child_id(task_id) if task_group else task_id
-        if not self.__from_mapped and task_group:
+        # Only apply task_group prefix if this operator was not created from a mapped operator
+        # Mapped operators already have the prefix applied during their creation
+        if task_group and not self.__from_mapped:
+            self.task_id = task_group.child_id(task_id)
             task_group.add(self)
+        else:
+            self.task_id = task_id
 
         super().__init__()
         self.task_group = task_group
diff --git a/task-sdk/tests/task_sdk/definitions/test_mappedoperator.py b/task-sdk/tests/task_sdk/definitions/test_mappedoperator.py
index 42d218c2c640a..30dec22e2554a 100644
--- a/task-sdk/tests/task_sdk/definitions/test_mappedoperator.py
+++ b/task-sdk/tests/task_sdk/definitions/test_mappedoperator.py
@@ -732,3 +732,25 @@ def test_setters(setter_name: str, old_value: object, new_value: object) -> None
     assert getattr(op, setter_name) == old_value
     setattr(op, setter_name, new_value)
     assert getattr(op, setter_name) == new_value
+
+
+def test_mapped_operator_in_task_group_no_duplicate_prefix():
+    """Test that task_id doesn't get duplicated prefix when unmapping a mapped operator in a task group."""
+    from airflow.sdk.definitions.taskgroup import TaskGroup
+
+    with DAG("test-dag"):
+        with TaskGroup(group_id="tg1") as tg1:
+            # Create a mapped task within the task group
+            mapped_task = MockOperator.partial(task_id="mapped_task", arg1="a").expand(arg2=["a", "b", "c"])
+
+    # Check the mapped operator has correct task_id
+    assert mapped_task.task_id == "tg1.mapped_task"
+    assert mapped_task.task_group == tg1
+    assert mapped_task.task_group.group_id == "tg1"
+
+    # Simulate what happens during execution - unmap the operator
+    # unmap expects resolved kwargs
+    unmapped = mapped_task.unmap({"arg2": "a"})
+
+    # The unmapped operator should have the same task_id, not a duplicate prefix
+    assert unmapped.task_id == "tg1.mapped_task", f"Expected 'tg1.mapped_task' but got '{unmapped.task_id}'"