diff --git a/reference/constraints/UniqueEntity.rst b/reference/constraints/UniqueEntity.rst
index 0e1731371a5..51c24c27cbd 100644
--- a/reference/constraints/UniqueEntity.rst
+++ b/reference/constraints/UniqueEntity.rst
@@ -402,4 +402,13 @@ blank, ``findBy()`` will be used. The method receives as its argument a
 fields configured in the ``fields`` option). The method should return a
 :phpfunction:`countable PHP variable <is_countable>`.
 
+.. warning::
+
+    This constraint does not support Doctrine types such as ``simple_array``,
+    ``json``, or ``jsonb``, nor does it handle association mappings like
+    ``One-To-Many`` and ``Many-To-Many`` relationships. It may also not work
+    correctly with custom Doctrine types. To perform uniqueness checks on
+    such fields, you must define a custom ``repositoryMethod`` that
+    implements the desired logic.
+
 .. _`race conditions`: https://en.wikipedia.org/wiki/Race_condition