diff --git a/mllib/src/main/scala/org/apache/spark/mllib/api/python/PythonMLLibAPI.scala b/mllib/src/main/scala/org/apache/spark/mllib/api/python/PythonMLLibAPI.scala
index 061db56c74938..bdf6ed9eb5b5d 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/api/python/PythonMLLibAPI.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/api/python/PythonMLLibAPI.scala
@@ -1473,7 +1473,11 @@ private[spark] object SerDe extends Serializable {
   initialize()
 
   def dumps(obj: AnyRef): Array[Byte] = {
-    new Pickler().dumps(obj)
+    obj match {
+      // Pickler in Python side cannot deserialize Scala Array normally. See SPARK-12834.
+      case array: Array[_] => new Pickler().dumps(array.toSeq.asJava)
+      case _ => new Pickler().dumps(obj)
+    }
   }
 
   def loads(bytes: Array[Byte]): AnyRef = {