diff --git a/native/spark-expr/src/datetime_funcs/date_diff.rs b/native/spark-expr/src/datetime_funcs/date_diff.rs
index 6a593f0f87..c39d2095e0 100644
--- a/native/spark-expr/src/datetime_funcs/date_diff.rs
+++ b/native/spark-expr/src/datetime_funcs/date_diff.rs
@@ -71,9 +71,22 @@ impl ScalarUDFImpl for SparkDateDiff {
     fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
         let [end_date, start_date] = take_function_args(self.name(), args.args)?;
 
-        // Convert scalars to arrays for uniform processing
-        let end_arr = end_date.into_array(1)?;
-        let start_arr = start_date.into_array(1)?;
+        // Determine target length (broadcast scalars to column length)
+        let len = match (&end_date, &start_date) {
+            (ColumnarValue::Array(a), _) => a.len(),
+            (_, ColumnarValue::Array(a)) => a.len(),
+            _ => 1,
+        };
+
+        // Convert both arguments to arrays of the same length
+        let end_arr = end_date.into_array(len)?;
+        let start_arr = start_date.into_array(len)?;
+
+        // Normalize dictionary arrays (important for Iceberg)
+        let end_arr = arrow::compute::cast(&end_arr, &DataType::Date32)
+            .map_err(|e| DataFusionError::Execution(e.to_string()))?;
+        let start_arr = arrow::compute::cast(&start_arr, &DataType::Date32)
+            .map_err(|e| DataFusionError::Execution(e.to_string()))?;
 
         let end_date_array = end_arr
             .as_any()
@@ -97,8 +110,4 @@ impl ScalarUDFImpl for SparkDateDiff {
 
         Ok(ColumnarValue::Array(Arc::new(result)))
     }
-
-    fn aliases(&self) -> &[String] {
-        &self.aliases
-    }
 }
diff --git a/spark/src/test/scala/org/apache/spark/sql/comet/ParquetDatetimeRebaseSuite.scala b/spark/src/test/scala/org/apache/spark/sql/comet/ParquetDatetimeRebaseSuite.scala
index bdb4a9d4b1..50ed6844ce 100644
--- a/spark/src/test/scala/org/apache/spark/sql/comet/ParquetDatetimeRebaseSuite.scala
+++ b/spark/src/test/scala/org/apache/spark/sql/comet/ParquetDatetimeRebaseSuite.scala
@@ -116,6 +116,33 @@ abstract class ParquetDatetimeRebaseSuite extends CometTestBase {
     }
   }
 
+  test("datediff works with dictionary-encoded timestamp columns") {
+    withTempPath { path =>
+      withSQLConf(
+        CometConf.COMET_NATIVE_SCAN_IMPL.key -> CometConf.SCAN_NATIVE_COMET,
+        CometConf.COMET_ENABLED.key -> "true",
+        "spark.sql.parquet.enableDictionary" -> "true") {
+        val df = spark
+          .createDataFrame(
+            Seq(
+              ("a", java.sql.Timestamp.valueOf("2024-01-02 10:00:00")),
+              ("b", java.sql.Timestamp.valueOf("2024-01-03 11:00:00"))))
+          .toDF("id", "ts")
+
+        df.write.mode("overwrite").parquet(path.getAbsolutePath)
+
+        val readDf = spark.read.parquet(path.getAbsolutePath)
+
+        val result = readDf
+          .selectExpr("datediff(current_date(), ts) as diff")
+          .collect()
+
+        // Just verify it executes correctly (no CometNativeException)
+        assert(result.length == 2)
+      }
+    }
+  }
+
   private def checkSparkNoRebaseAnswer(df: => DataFrame): Unit = {
     var expected: Array[Row] = Array.empty