diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/BroadcastJoinOuterJoinStreamSide.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/BroadcastJoinOuterJoinStreamSide.scala
index 5aab2f3b6d358..c6d6a9adf72e5 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/BroadcastJoinOuterJoinStreamSide.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/BroadcastJoinOuterJoinStreamSide.scala
@@ -36,7 +36,8 @@ object BroadcastJoinOuterJoinStreamSide extends Rule[LogicalPlan] with JoinSelec
           LeftOuter | LeftSemi | LeftAnti, _, _) =>
           j
         case j @ ExtractEquiJoinKeys(LeftOuter | LeftSemi | LeftAnti,
-          leftKeys, _, None, left, right, hint) if leftKeys.nonEmpty && muchSmaller(left, right) &&
+          leftKeys, _, None, left, right, hint)
+          if leftKeys.nonEmpty && muchSmaller(left, right, conf) &&
           !(hintToBroadcastRight(hint) || canBroadcastBySize(right, conf)) &&
           (hintToBroadcastLeft(hint) || canBroadcastBySize(left, conf)) =>
           logInfo("BroadcastJoinOuterJoinStreamSide detected.")
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/joins.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/joins.scala
index 70c60f5124551..60e5569480419 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/joins.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/joins.scala
@@ -26,6 +26,7 @@ import org.apache.spark.sql.catalyst.plans._
 import org.apache.spark.sql.catalyst.plans.logical._
 import org.apache.spark.sql.catalyst.rules._
 import org.apache.spark.sql.internal.SQLConf
+import org.apache.spark.util.Utils
 
 /**
  * Reorder the joins and push all the conditions into join, so that the bottom ones have at least
@@ -270,28 +271,18 @@ trait JoinSelectionHelper {
     val buildLeft = if (hintOnly) {
       hintToShuffleHashJoinLeft(hint)
     } else {
-      if (hintToPreferShuffleHashJoinLeft(hint)) {
-        true
-      } else {
-        if (!conf.preferSortMergeJoin) {
-          canBuildLocalHashMapBySize(left, conf) && muchSmaller(left, right)
-        } else {
-          false
-        }
-      }
+      hintToPreferShuffleHashJoinLeft(hint) ||
+        (!conf.preferSortMergeJoin && canBuildLocalHashMapBySize(left, conf) &&
+          muchSmaller(left, right)) ||
+        forceApplyShuffledHashJoin(conf)
     }
     val buildRight = if (hintOnly) {
       hintToShuffleHashJoinRight(hint)
     } else {
-      if (hintToPreferShuffleHashJoinRight(hint)) {
-        true
-      } else {
-        if (!conf.preferSortMergeJoin) {
-          canBuildLocalHashMapBySize(right, conf) && muchSmaller(right, left)
-        } else {
-          false
-        }
-      }
+      hintToPreferShuffleHashJoinRight(hint) ||
+        (!conf.preferSortMergeJoin && canBuildLocalHashMapBySize(right, conf) &&
+          muchSmaller(right, left)) ||
+        forceApplyShuffledHashJoin(conf)
     }
     getBuildSide(
       canBuildShuffledHashJoinLeft(joinType) && buildLeft,
@@ -435,8 +426,8 @@ trait JoinSelectionHelper {
    * that is much smaller than other one. Since we does not have the statistic for number of rows,
    * use the size of bytes here as estimation.
    */
-  def muchSmaller(a: LogicalPlan, b: LogicalPlan): Boolean = {
-    a.stats.sizeInBytes * 3 <= b.stats.sizeInBytes
+  def muchSmaller(a: LogicalPlan, b: LogicalPlan, conf: SQLConf): Boolean = {
+    a.stats.sizeInBytes * conf.getConf(SQLConf.SHUFFLE_HASH_JOIN_FACTOR) <= b.stats.sizeInBytes
   }
 
   def canBroadcastTokenTree(left: LogicalPlan,
@@ -460,5 +451,14 @@ trait JoinSelectionHelper {
         right.stats.sizeInBytes <= conf.containsJoinThreshold &&
         !hintToNotBroadcastRight(hint)
   }
+
+  /**
+   * Returns whether a shuffled hash join should be force applied.
+   * The config key is hard-coded because it's testing only and should not be exposed.
+   */
+  private def forceApplyShuffledHashJoin(conf: SQLConf): Boolean = {
+    Utils.isTesting &&
+      conf.getConfString("spark.sql.join.forceApplyShuffledHashJoin", "false") == "true"
+  }
 }
 
diff --git a/sql/core/src/test/resources/sql-tests/inputs/postgreSQL/join.sql b/sql/core/src/test/resources/sql-tests/inputs/postgreSQL/join.sql
index cc07b00cc3670..1a8ecbbe4178a 100644
--- a/sql/core/src/test/resources/sql-tests/inputs/postgreSQL/join.sql
+++ b/sql/core/src/test/resources/sql-tests/inputs/postgreSQL/join.sql
@@ -13,7 +13,7 @@
 
 --CONFIG_DIM1 spark.sql.autoBroadcastJoinThreshold=10485760
 --CONFIG_DIM1 spark.sql.autoBroadcastJoinThreshold=-1,spark.sql.join.preferSortMergeJoin=true
---CONFIG_DIM1 spark.sql.autoBroadcastJoinThreshold=-1,spark.sql.join.preferSortMergeJoin=false
+--CONFIG_DIM1 spark.sql.autoBroadcastJoinThreshold=-1,spark.sql.join.forceApplyShuffledHashJoin=true
 
 --CONFIG_DIM2 spark.sql.codegen.wholeStage=true
 --CONFIG_DIM2 spark.sql.codegen.wholeStage=false,spark.sql.codegen.factoryMode=CODEGEN_ONLY
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala
index ecd3e3c44c84d..876ef38f3b8f7 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala
@@ -1603,4 +1603,12 @@ class JoinSuite extends QueryTest with SharedSparkSession with AdaptiveSparkPlan
       }
     }
   }
+
+  test("SPARK-35984: Config to force applying shuffled hash join") {
+    val sql = "SELECT * FROM testData JOIN testData2 ON key = a"
+    assertJoin(sql, classOf[SortMergeJoinExec])
+    withSQLConf("spark.sql.join.forceApplyShuffledHashJoin" -> "true") {
+      assertJoin(sql, classOf[ShuffledHashJoinExec])
+    }
+  }
 }