diff --git a/onnxruntime/core/framework/tensorprotoutils.cc b/onnxruntime/core/framework/tensorprotoutils.cc
index 4b4a661fdf..89726f5a4c 100644
--- a/onnxruntime/core/framework/tensorprotoutils.cc
+++ b/onnxruntime/core/framework/tensorprotoutils.cc
@@ -538,7 +538,7 @@ TensorProto::DataType GetTensorProtoType(const Tensor& tensor) {
 }
 
 ONNX_NAMESPACE::TensorProto TensorToTensorProto(const Tensor& tensor, const std::string& tensor_proto_name,
-                                                const onnx::TypeProto& tensor_proto_type) {
+                                                const ONNX_NAMESPACE::TypeProto& tensor_proto_type) {
   // Given we are using the raw_data field in the protobuf, this will work only for little-endian format.
   ORT_ENFORCE(IsLittleEndianOrder());
 
diff --git a/onnxruntime/core/framework/tensorprotoutils.h b/onnxruntime/core/framework/tensorprotoutils.h
index 6be46a8a06..15d70f35ed 100644
--- a/onnxruntime/core/framework/tensorprotoutils.h
+++ b/onnxruntime/core/framework/tensorprotoutils.h
@@ -47,7 +47,7 @@ ONNX_NAMESPACE::TensorProto::DataType GetTensorProtoType(const Tensor& tensor);
     TODO Once the GetTensorProtoType supports all data types, we can remove the tensor_proto_type parameter and 
     instead get the type from the tensor. */
 ONNX_NAMESPACE::TensorProto TensorToTensorProto(const Tensor& tensor, const std::string& tensor_proto_name,
-                                                const onnx::TypeProto& tensor_proto_type);
+                                                const ONNX_NAMESPACE::TypeProto& tensor_proto_type);
 
 ONNXTensorElementDataType CApiElementTypeFromProtoType(int type);
 ONNXTensorElementDataType GetTensorElementType(const ONNX_NAMESPACE::TensorProto& tensor_proto);
diff --git a/onnxruntime/core/graph/graph_utils.cc b/onnxruntime/core/graph/graph_utils.cc
index 15d2613b99..2ac2a15303 100644
--- a/onnxruntime/core/graph/graph_utils.cc
+++ b/onnxruntime/core/graph/graph_utils.cc
@@ -398,7 +398,7 @@ const ONNX_NAMESPACE::TensorProto* GetConstantInitializer(const Graph& graph, co
 }
 
 bool IsConstantInitializer(const Graph& graph, const std::string& initializer_name, bool check_outer_scope) {
-  const onnx::TensorProto* initializer = GetConstantInitializer(graph, initializer_name, check_outer_scope);
+  const ONNX_NAMESPACE::TensorProto* initializer = GetConstantInitializer(graph, initializer_name, check_outer_scope);
   return initializer != nullptr;
 }
 
diff --git a/onnxruntime/test/optimizer/optimizer_test.cc b/onnxruntime/test/optimizer/optimizer_test.cc
index fce027650f..b8422cd1d9 100644
--- a/onnxruntime/test/optimizer/optimizer_test.cc
+++ b/onnxruntime/test/optimizer/optimizer_test.cc
@@ -20,8 +20,6 @@
 using namespace std;
 using namespace ONNX_NAMESPACE;
 
-using namespace onnx;
-
 namespace onnxruntime {
 namespace test {
 
@@ -48,7 +46,7 @@ TEST(OptimizerTest, Basic) {
 
     initializer_tensor[i].set_name(inputs[i]->Name());
     initializer_tensor[i].add_dims(tensor_dim);
-    initializer_tensor[i].set_data_type(onnx::TensorProto_DataType_INT32);
+    initializer_tensor[i].set_data_type(ONNX_NAMESPACE::TensorProto_DataType_INT32);
     for (int j = 0; j < tensor_dim; j++) {
       initializer_tensor[i].add_int32_data((i + 1) * j);
     }
diff --git a/onnxruntime/test/providers/memcpy_test.cc b/onnxruntime/test/providers/memcpy_test.cc
index e502a02724..c43779875f 100644
--- a/onnxruntime/test/providers/memcpy_test.cc
+++ b/onnxruntime/test/providers/memcpy_test.cc
@@ -31,7 +31,7 @@ TEST(MemcpyTest, copy1) {
   KernelRegistryManager kernel_registry_manager;
   kernel_registry_manager.RegisterKernels(execution_providers);
 
-  onnx::ModelProto mp;
+  ONNX_NAMESPACE::ModelProto mp;
   std::ifstream model_istream("testdata/matmul_1.onnx", std::ifstream::in | std::ifstream::binary);
   google::protobuf::io::IstreamInputStream zero_copy_input(&model_istream);
   const bool result = mp.ParseFromZeroCopyStream(&zero_copy_input) && model_istream.eof();