diff --git a/python/pyspark/sql/tests/test_types.py b/python/pyspark/sql/tests/test_types.py
index c6e70da1f8dc..b038cf6ce5ba 100644
--- a/python/pyspark/sql/tests/test_types.py
+++ b/python/pyspark/sql/tests/test_types.py
@@ -1579,6 +1579,13 @@ def test_row_without_field_sorting(self):
         self.assertEqual(r, expected)
         self.assertEqual(repr(r), "Row(b=1, a=2)")
 
+    def test_struct_field_from_json(self):
+        # SPARK-40820: fromJson with only name and type
+        json = {"name": "c1", "type": "string"}
+        struct_field = StructField.fromJson(json)
+
+        self.assertEqual(repr(struct_field), "StructField('c1', StringType(), True)")
+
 
 class TypesTests(TypesTestsMixin, ReusedSQLTestCase):
     pass
diff --git a/python/pyspark/sql/types.py b/python/pyspark/sql/types.py
index 01db75b25003..84a4e7935415 100644
--- a/python/pyspark/sql/types.py
+++ b/python/pyspark/sql/types.py
@@ -769,8 +769,8 @@ def fromJson(cls, json: Dict[str, Any]) -> "StructField":
         return StructField(
             json["name"],
             _parse_datatype_json_value(json["type"]),
-            json["nullable"],
-            json["metadata"],
+            json.get("nullable", True),
+            json.get("metadata"),
         )
 
     def needConversion(self) -> bool:
diff --git a/sql/api/src/main/scala/org/apache/spark/sql/types/DataType.scala b/sql/api/src/main/scala/org/apache/spark/sql/types/DataType.scala
index 2bd88d597563..5f563e3b7a8f 100644
--- a/sql/api/src/main/scala/org/apache/spark/sql/types/DataType.scala
+++ b/sql/api/src/main/scala/org/apache/spark/sql/types/DataType.scala
@@ -258,6 +258,11 @@ object DataType {
     ("nullable", JBool(nullable)),
     ("type", dataType: JValue)) =>
       StructField(name, parseDataType(dataType), nullable)
+    // Support reading schema when 'nullable' is missing.
+    case JSortedObject(
+    ("name", JString(name)),
+    ("type", dataType: JValue)) =>
+      StructField(name, parseDataType(dataType))
     case other =>
       throw new IllegalArgumentException(
         s"Failed to convert the JSON string '${compact(render(other))}' to a field.")
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/types/DataTypeSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/types/DataTypeSuite.scala
index 0e78f875ad7c..6daeda693002 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/types/DataTypeSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/types/DataTypeSuite.scala
@@ -317,6 +317,29 @@ class DataTypeSuite extends SparkFunSuite {
     assert(message.contains("Unrecognized token 'abcd'"))
   }
 
+  // SPARK-40820: fromJson with only name and type
+  test("Deserialized and serialized schema without nullable or metadata in") {
+    val schema =
+      """
+        |{
+        |    "type": "struct",
+        |    "fields": [
+        |        {
+        |            "name": "c1",
+        |            "type": "string"
+        |        }
+        |    ]
+        |}
+        |""".stripMargin
+    val dt = DataType.fromJson(schema)
+
+    dt.simpleString equals "struct<c1:string>"
+    dt.json equals
+      """
+        |{"type":"struct","fields":[{"name":"c1","type":"string","nullable":false,"metadata":{}}]}
+        |""".stripMargin
+  }
+
   def checkDefaultSize(dataType: DataType, expectedDefaultSize: Int): Unit = {
     test(s"Check the default size of $dataType") {
       assert(dataType.defaultSize === expectedDefaultSize)