diff --git a/backends-velox/src/main/scala/org/apache/spark/sql/execution/ColumnarBuildSideRelation.scala b/backends-velox/src/main/scala/org/apache/spark/sql/execution/ColumnarBuildSideRelation.scala
index 59a9cb2b00fc..d542fd92b92c 100644
--- a/backends-velox/src/main/scala/org/apache/spark/sql/execution/ColumnarBuildSideRelation.scala
+++ b/backends-velox/src/main/scala/org/apache/spark/sql/execution/ColumnarBuildSideRelation.scala
@@ -33,6 +33,7 @@ import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.utils.SparkArrowUtil
 import org.apache.spark.sql.vectorized.ColumnarBatch
 import org.apache.spark.task.TaskResources
+import org.apache.spark.util.KnownSizeEstimation
 
 import org.apache.arrow.c.ArrowSchema
 
@@ -61,7 +62,8 @@ case class ColumnarBuildSideRelation(
     output: Seq[Attribute],
     batches: Array[Array[Byte]],
     safeBroadcastMode: SafeBroadcastMode)
-  extends BuildSideRelation {
+  extends BuildSideRelation
+  with KnownSizeEstimation {
 
   // Rebuild the real BroadcastMode on demand; never serialize it.
   @transient override lazy val mode: BroadcastMode =
@@ -236,4 +238,11 @@ case class ColumnarBuildSideRelation(
     }
     iterator.toArray
   }
+  override def estimatedSize: Long = {
+    if (batches != null) {
+      batches.map(_.length.toLong).sum
+    } else {
+      0L
+    }
+  }
 }
diff --git a/backends-velox/src/main/scala/org/apache/spark/sql/execution/unsafe/UnsafeColumnarBuildSideRelation.scala b/backends-velox/src/main/scala/org/apache/spark/sql/execution/unsafe/UnsafeColumnarBuildSideRelation.scala
index 80e92a1537e8..308834657a00 100644
--- a/backends-velox/src/main/scala/org/apache/spark/sql/execution/unsafe/UnsafeColumnarBuildSideRelation.scala
+++ b/backends-velox/src/main/scala/org/apache/spark/sql/execution/unsafe/UnsafeColumnarBuildSideRelation.scala
@@ -36,7 +36,7 @@ import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.utils.SparkArrowUtil
 import org.apache.spark.sql.vectorized.ColumnarBatch
 import org.apache.spark.task.TaskResources
-import org.apache.spark.util.Utils
+import org.apache.spark.util.{KnownSizeEstimation, Utils}
 
 import com.esotericsoftware.kryo.{Kryo, KryoSerializable}
 import com.esotericsoftware.kryo.io.{Input, Output}
@@ -102,7 +102,8 @@ case class UnsafeColumnarBuildSideRelation(
   extends BuildSideRelation
   with Externalizable
   with Logging
-  with KryoSerializable {
+  with KryoSerializable
+  with KnownSizeEstimation {
 
   // Rebuild the real BroadcastMode on demand; never serialize it.
   @transient override lazy val mode: BroadcastMode =
@@ -366,4 +367,12 @@ case class UnsafeColumnarBuildSideRelation(
     }
     iterator.toArray
   }
+
+  override def estimatedSize: Long = {
+    if (batches != null) {
+      batches.totalBytes
+    } else {
+      0L
+    }
+  }
 }