diff --git a/BUILD.gn b/BUILD.gn
index 372d8c39db..11a1c8ad94 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1024,6 +1024,7 @@ source_set("tint_unittests_hlsl_writer_src") {
     "src/writer/hlsl/generator_impl_identifier_test.cc",
     "src/writer/hlsl/generator_impl_return_test.cc",
     "src/writer/hlsl/generator_impl_test.cc",
+    "src/writer/hlsl/generator_impl_unary_op_test.cc",
     "src/writer/hlsl/namer_test.cc",
   ]
 
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index ca0f3ec2ce..a67b67447d 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -548,6 +548,7 @@ if (${TINT_BUILD_HLSL_WRITER})
     writer/hlsl/generator_impl_identifier_test.cc
     writer/hlsl/generator_impl_return_test.cc
     writer/hlsl/generator_impl_test.cc
+    writer/hlsl/generator_impl_unary_op_test.cc
     writer/hlsl/namer_test.cc
   )
 endif()
diff --git a/src/writer/hlsl/generator_impl.cc b/src/writer/hlsl/generator_impl.cc
index 076aa7ba25..741110fc32 100644
--- a/src/writer/hlsl/generator_impl.cc
+++ b/src/writer/hlsl/generator_impl.cc
@@ -17,6 +17,7 @@
 #include "src/ast/binary_expression.h"
 #include "src/ast/identifier_expression.h"
 #include "src/ast/return_statement.h"
+#include "src/ast/unary_op_expression.h"
 
 namespace tint {
 namespace writer {
@@ -157,6 +158,9 @@ bool GeneratorImpl::EmitExpression(ast::Expression* expr) {
   if (expr->IsIdentifier()) {
     return EmitIdentifier(expr->AsIdentifier());
   }
+  if (expr->IsUnaryOp()) {
+    return EmitUnaryOp(expr->AsUnaryOp());
+  }
 
   error_ = "unknown expression type: " + expr->str();
   return false;
@@ -228,6 +232,26 @@ bool GeneratorImpl::EmitStatement(ast::Statement* stmt) {
   return false;
 }
 
+bool GeneratorImpl::EmitUnaryOp(ast::UnaryOpExpression* expr) {
+  switch (expr->op()) {
+    case ast::UnaryOp::kNot:
+      out_ << "!";
+      break;
+    case ast::UnaryOp::kNegation:
+      out_ << "-";
+      break;
+  }
+  out_ << "(";
+
+  if (!EmitExpression(expr->expr())) {
+    return false;
+  }
+
+  out_ << ")";
+
+  return true;
+}
+
 }  // namespace hlsl
 }  // namespace writer
 }  // namespace tint
diff --git a/src/writer/hlsl/generator_impl.h b/src/writer/hlsl/generator_impl.h
index b6565ead27..095165c581 100644
--- a/src/writer/hlsl/generator_impl.h
+++ b/src/writer/hlsl/generator_impl.h
@@ -63,6 +63,10 @@ class GeneratorImpl : public TextGenerator {
   /// @param stmt the statement to emit
   /// @returns true if the statement was emitted
   bool EmitStatement(ast::Statement* stmt);
+  /// Handles a unary op expression
+  /// @param expr the expression to emit
+  /// @returns true if the expression was emitted
+  bool EmitUnaryOp(ast::UnaryOpExpression* expr);
 
   /// Checks if the global variable is in an input or output struct
   /// @param var the variable to check
diff --git a/src/writer/hlsl/generator_impl_unary_op_test.cc b/src/writer/hlsl/generator_impl_unary_op_test.cc
new file mode 100644
index 0000000000..4f9317745f
--- /dev/null
+++ b/src/writer/hlsl/generator_impl_unary_op_test.cc
@@ -0,0 +1,58 @@
+// Copyright 2020 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <memory>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "src/ast/identifier_expression.h"
+#include "src/ast/module.h"
+#include "src/ast/unary_op_expression.h"
+#include "src/writer/hlsl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace hlsl {
+namespace {
+
+struct UnaryOpData {
+  const char* name;
+  ast::UnaryOp op;
+};
+inline std::ostream& operator<<(std::ostream& out, UnaryOpData data) {
+  out << data.op;
+  return out;
+}
+using HlslUnaryOpTest = testing::TestWithParam<UnaryOpData>;
+TEST_P(HlslUnaryOpTest, Emit) {
+  auto params = GetParam();
+
+  auto expr = std::make_unique<ast::IdentifierExpression>("expr");
+  ast::UnaryOpExpression op(params.op, std::move(expr));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  ASSERT_TRUE(g.EmitExpression(&op)) << g.error();
+  EXPECT_EQ(g.result(), std::string(params.name) + "(expr)");
+}
+INSTANTIATE_TEST_SUITE_P(HlslGeneratorImplTest,
+                         HlslUnaryOpTest,
+                         testing::Values(UnaryOpData{"!", ast::UnaryOp::kNot},
+                                         UnaryOpData{"-",
+                                                     ast::UnaryOp::kNegation}));
+
+}  // namespace
+}  // namespace hlsl
+}  // namespace writer
+}  // namespace tint