diff --git a/mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp b/mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp
--- a/mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp
+++ b/mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp
@@ -285,6 +285,11 @@
     printer << " " << ParallelOp::getNumWorkersKeyword() << "(" << numWorkers
             << ")";
 
+  // vector_length()?
+  if (auto vectorLength = op.vectorLength())
+    printer << " " << ParallelOp::getVectorLengthKeyword() << "("
+            << vectorLength << ")";
+
   // if()?
   if (Value ifCond = op.ifCond())
     printer << " " << ParallelOp::getIfKeyword() << "(" << ifCond << ")";
diff --git a/mlir/test/Dialect/OpenACC/ops.mlir b/mlir/test/Dialect/OpenACC/ops.mlir
--- a/mlir/test/Dialect/OpenACC/ops.mlir
+++ b/mlir/test/Dialect/OpenACC/ops.mlir
@@ -232,3 +232,15 @@
 // CHECK-NEXT: }
 // CHECK-NEXT: acc.loop tile([[TILESIZE]]: i64, [[TILESIZE]]: i64) {
 // CHECK-NEXT: }
+
+
+func @testparallelop() -> () {
+  %vectorLength = constant 128 : index
+  acc.parallel vector_length(%vectorLength) {
+  }
+  return
+}
+
+// CHECK:      [[VECTORLENGTH:%.*]] = constant 128 : index
+// CHECK-NEXT: acc.parallel vector_length([[VECTORLENGTH]]) {
+// CHECK-NEXT: }