diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
index 35c7f00d4e42a..21d646f4299dd 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
@@ -69,6 +69,7 @@ trait HiveTypeCoercion {
   val typeCoercionRules =
     PropagateTypes ::
     ConvertNaNs ::
+    InConversion ::
     WidenTypes ::
     PromoteStrings ::
     DecimalPrecision ::
@@ -280,6 +281,16 @@ trait HiveTypeCoercion {
     }
   }
 
+  /**
+   * Convert all expressions in in() list to the left operator type
+   */
+  object InConversion extends Rule[LogicalPlan] {
+    def apply(plan: LogicalPlan): LogicalPlan = plan transformAllExpressions {
+      case i @ In(a, b) if b.exists(_.dataType != a.dataType) =>
+        i.makeCopy(Array(a, b.map(Cast(_, a.dataType))))
+    }
+  }
+
   // scalastyle:off
   /**
    * Calculates and propagates precision for fixed-precision decimals. Hive has a number of
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
index 2d03fbfb0d311..9dc6f3c398ae1 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
@@ -308,8 +308,8 @@ object OptimizeIn extends Rule[LogicalPlan] {
   def apply(plan: LogicalPlan): LogicalPlan = plan transform {
     case q: LogicalPlan => q transformExpressionsDown {
       case In(v, list) if !list.exists(!_.isInstanceOf[Literal]) =>
-          val hSet = list.map(e => e.eval(null))
-          InSet(v, HashSet() ++ hSet)
+        val hSet = list.map(e => e.eval(null))
+        InSet(v, HashSet() ++ hSet)
     }
   }
 }
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
index 9e02e69fda3f2..84d70e4a1eb7d 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
@@ -88,6 +88,15 @@ class SQLQuerySuite extends QueryTest with BeforeAndAfterAll {
       Row(1, 1) :: Nil)
   }
 
+  test("SPARK-6201 IN type conversion") {
+    jsonRDD(sparkContext.parallelize(Seq("{\"a\": \"1\"}}", "{\"a\": \"2\"}}", "{\"a\": \"3\"}}")))
+      .registerTempTable("d")
+
+    checkAnswer(
+      sql("select * from d where d.a in (1,2)"),
+      Seq(Row("1"), Row("2")))
+  }
+
   test("SPARK-3176 Added Parser of SQL ABS()") {
     checkAnswer(
       sql("SELECT ABS(-1.3)"),