diff --git a/fluss-lake/fluss-lake-iceberg/src/main/java/org/apache/fluss/lake/iceberg/IcebergLakeCatalog.java b/fluss-lake/fluss-lake-iceberg/src/main/java/org/apache/fluss/lake/iceberg/IcebergLakeCatalog.java
index 9ca70b12622..7db0a1957a0 100644
--- a/fluss-lake/fluss-lake-iceberg/src/main/java/org/apache/fluss/lake/iceberg/IcebergLakeCatalog.java
+++ b/fluss-lake/fluss-lake-iceberg/src/main/java/org/apache/fluss/lake/iceberg/IcebergLakeCatalog.java
@@ -92,6 +92,13 @@ protected Catalog getIcebergCatalog() {
     @Override
     public void createTable(TablePath tablePath, TableDescriptor tableDescriptor, Context context)
             throws TableAlreadyExistException {
+        // validate at most one key field requirement
+        List<String> keys = tableDescriptor.getBucketKeys();
+        checkArgument(
+                keys.size() <= 1,
+                "Iceberg format supports at most one bucket key, but got: %s",
+                keys);
+
         // convert Fluss table path to iceberg table
         boolean isPkTable = tableDescriptor.hasPrimaryKey();
         TableIdentifier icebergId = toIcebergTableIdentifier(tablePath);
diff --git a/fluss-lake/fluss-lake-iceberg/src/test/java/org/apache/fluss/lake/iceberg/IcebergLakeCatalogTest.java b/fluss-lake/fluss-lake-iceberg/src/test/java/org/apache/fluss/lake/iceberg/IcebergLakeCatalogTest.java
index 991a3286884..30f2b82f1c0 100644
--- a/fluss-lake/fluss-lake-iceberg/src/test/java/org/apache/fluss/lake/iceberg/IcebergLakeCatalogTest.java
+++ b/fluss-lake/fluss-lake-iceberg/src/test/java/org/apache/fluss/lake/iceberg/IcebergLakeCatalogTest.java
@@ -290,8 +290,8 @@ void rejectsPrimaryKeyTableWithMultipleBucketKeys() {
                                         tablePath,
                                         tableDescriptor,
                                         new TestingLakeCatalogContext()))
-                .isInstanceOf(UnsupportedOperationException.class)
-                .hasMessageContaining("Only one bucket key is supported for Iceberg");
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("Iceberg format supports at most one bucket key");
     }
 
     @Test
@@ -442,8 +442,8 @@ void rejectsLogTableWithMultipleBucketKeys() {
                                         tablePath,
                                         tableDescriptor,
                                         new TestingLakeCatalogContext()))
-                .isInstanceOf(UnsupportedOperationException.class)
-                .hasMessageContaining("Only one bucket key is supported for Iceberg");
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("Iceberg format supports at most one bucket key");
     }
 
     @ParameterizedTest