diff --git a/python/pyspark/sql/types.py b/python/pyspark/sql/types.py
index 920cf009f599d..aaf520fa8019f 100644
--- a/python/pyspark/sql/types.py
+++ b/python/pyspark/sql/types.py
@@ -483,7 +483,9 @@ def __init__(self, fields=None):
             self.names = [f.name for f in fields]
             assert all(isinstance(f, StructField) for f in fields),\
                 "fields should be a list of StructField"
-        self._needSerializeAnyField = any(f.needConversion() for f in self)
+        # Precalculated list of fields that need conversion with fromInternal/toInternal functions
+        self._needConversion = [f.needConversion() for f in self]
+        self._needSerializeAnyField = any(self._needConversion)
 
     def add(self, field, data_type=None, nullable=True, metadata=None):
         """
@@ -528,7 +530,9 @@ def add(self, field, data_type=None, nullable=True, metadata=None):
                 data_type_f = data_type
             self.fields.append(StructField(field, data_type_f, nullable, metadata))
             self.names.append(field)
-        self._needSerializeAnyField = any(f.needConversion() for f in self)
+        # Precalculated list of fields that need conversion with fromInternal/toInternal functions
+        self._needConversion = [f.needConversion() for f in self]
+        self._needSerializeAnyField = any(self._needConversion)
         return self
 
     def __iter__(self):
@@ -590,13 +594,17 @@ def toInternal(self, obj):
             return
 
         if self._needSerializeAnyField:
+            # Only calling toInternal function for fields that need conversion
             if isinstance(obj, dict):
-                return tuple(f.toInternal(obj.get(n)) for n, f in zip(self.names, self.fields))
+                return tuple(f.toInternal(obj.get(n)) if c else obj.get(n)
+                             for n, f, c in zip(self.names, self.fields, self._needConversion))
             elif isinstance(obj, (tuple, list)):
-                return tuple(f.toInternal(v) for f, v in zip(self.fields, obj))
+                return tuple(f.toInternal(v) if c else v
+                             for f, v, c in zip(self.fields, obj, self._needConversion))
             elif hasattr(obj, "__dict__"):
                 d = obj.__dict__
-                return tuple(f.toInternal(d.get(n)) for n, f in zip(self.names, self.fields))
+                return tuple(f.toInternal(d.get(n)) if c else d.get(n)
+                             for n, f, c in zip(self.names, self.fields, self._needConversion))
             else:
                 raise ValueError("Unexpected tuple %r with StructType" % obj)
         else:
@@ -619,7 +627,9 @@ def fromInternal(self, obj):
             # it's already converted by pickler
             return obj
         if self._needSerializeAnyField:
-            values = [f.fromInternal(v) for f, v in zip(self.fields, obj)]
+            # Only calling fromInternal function for fields that need conversion
+            values = [f.fromInternal(v) if c else v
+                      for f, v, c in zip(self.fields, obj, self._needConversion)]
         else:
             values = obj
         return _create_row(self.names, values)