diff --git a/mlir/lib/Conversion/ComplexToLLVM/ComplexToLLVM.cpp b/mlir/lib/Conversion/ComplexToLLVM/ComplexToLLVM.cpp
--- a/mlir/lib/Conversion/ComplexToLLVM/ComplexToLLVM.cpp
+++ b/mlir/lib/Conversion/ComplexToLLVM/ComplexToLLVM.cpp
@@ -78,6 +78,18 @@
   }
 };
 
+struct ConstantOpLowering : public ConvertOpToLLVMPattern<complex::ConstantOp> {
+  using ConvertOpToLLVMPattern::ConvertOpToLLVMPattern;
+
+  LogicalResult
+  matchAndRewrite(complex::ConstantOp op, OpAdaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const override {
+    return LLVM::detail::oneToOneRewrite(
+        op, LLVM::ConstantOp::getOperationName(), adaptor.getOperands(),
+        *getTypeConverter(), rewriter);
+  }
+};
+
 struct CreateOpConversion : public ConvertOpToLLVMPattern<complex::CreateOp> {
   using ConvertOpToLLVMPattern<complex::CreateOp>::ConvertOpToLLVMPattern;
 
@@ -294,6 +306,7 @@
   patterns.add<
       AbsOpConversion,
       AddOpConversion,
+      ConstantOpLowering,
       CreateOpConversion,
       DivOpConversion,
       ImOpConversion,
diff --git a/mlir/test/Conversion/ComplexToLLVM/convert-to-llvm.mlir b/mlir/test/Conversion/ComplexToLLVM/convert-to-llvm.mlir
--- a/mlir/test/Conversion/ComplexToLLVM/convert-to-llvm.mlir
+++ b/mlir/test/Conversion/ComplexToLLVM/convert-to-llvm.mlir
@@ -10,6 +10,13 @@
   return %cplx2 : complex<f32>
 }
 
+// CHECK-LABEL: func @complex_constant
+// CHECK-NEXT:    llvm.mlir.constant([1.000000e+00, 2.000000e+00]) : !llvm.struct<(f64, f64)>
+func @complex_constant() -> complex<f64> {
+  %cplx2 = complex.constant [1.000000e+00, 2.000000e+00] : complex<f64>
+  return %cplx2 : complex<f64>
+}
+
 // CHECK-LABEL: func @complex_extract
 // CHECK-SAME:    (%[[CPLX:.*]]: complex<f32>)
 // CHECK-NEXT:    %[[CAST0:.*]] = builtin.unrealized_conversion_cast %[[CPLX]] : complex<f32> to !llvm.struct<(f32, f32)>