diff --git a/src/sage/rings/function_field/element.pyx b/src/sage/rings/function_field/element.pyx
index 5e8254e8294..c0fa24036bd 100644
--- a/src/sage/rings/function_field/element.pyx
+++ b/src/sage/rings/function_field/element.pyx
@@ -80,6 +80,10 @@ def is_FunctionFieldElement(x):
         sage: sage.rings.function_field.element.is_FunctionFieldElement(0)
         False
     """
+    from sage.misc.superseded import deprecation_cython
+    deprecation_cython(38289,
+                       "The function is_FunctionFieldElement is deprecated; "
+                       "use '....parent() in FunctionFields()' instead.")
     if isinstance(x, FunctionFieldElement):
         return True
     from sage.rings.function_field.function_field import is_FunctionField