diff --git a/python/docs/source/migration_guide/pyspark_upgrade.rst b/python/docs/source/migration_guide/pyspark_upgrade.rst
index 17c888be959df..49872fb197af3 100644
--- a/python/docs/source/migration_guide/pyspark_upgrade.rst
+++ b/python/docs/source/migration_guide/pyspark_upgrade.rst
@@ -67,6 +67,7 @@ Upgrading from PySpark 3.5 to 4.0
 * In Spark 4.0, ``DataFrame.to_pandas_on_spark`` has been removed from PySpark, use ``DataFrame.pandas_api`` instead.
 * In Spark 4.0, ``DatatimeIndex.week`` and ``DatatimeIndex.weekofyear`` have been removed from Pandas API on Spark, use ``DatetimeIndex.isocalendar().week`` instead.
 * In Spark 4.0, ``Series.dt.week`` and ``Series.dt.weekofyear`` have been removed from Pandas API on Spark, use ``Series.dt.isocalendar().week`` instead.
+* In Spark 4.0, when applying ``astype`` to a decimal type object, the existing missing value is changed to ``True`` instead of ``False`` from Pandas API on Spark.