diff --git a/atom/browser/net/atom_url_loader_factory.cc b/atom/browser/net/atom_url_loader_factory.cc
index 2acfa03cf9..331b82914c 100644
--- a/atom/browser/net/atom_url_loader_factory.cc
+++ b/atom/browser/net/atom_url_loader_factory.cc
@@ -372,6 +372,10 @@ void AtomURLLoaderFactory::StartLoadingHttp(
   if (!dict.Get("method", &request->method))
     request->method = original_request.method;
 
+  base::DictionaryValue upload_data;
+  if (request->method != "GET" && request->method != "HEAD")
+    dict.Get("uploadData", &upload_data);
+
   scoped_refptr<AtomBrowserContext> browser_context =
       AtomBrowserContext::From("", false);
   v8::Local<v8::Value> value;
@@ -393,7 +397,8 @@ void AtomURLLoaderFactory::StartLoadingHttp(
   new URLPipeLoader(
       url_loader_factory, std::move(request), std::move(loader),
       std::move(client),
-      static_cast<net::NetworkTrafficAnnotationTag>(traffic_annotation));
+      static_cast<net::NetworkTrafficAnnotationTag>(traffic_annotation),
+      std::move(upload_data));
 }
 
 // static
diff --git a/atom/browser/net/url_pipe_loader.cc b/atom/browser/net/url_pipe_loader.cc
index a75d796005..c3f0f3f367 100644
--- a/atom/browser/net/url_pipe_loader.cc
+++ b/atom/browser/net/url_pipe_loader.cc
@@ -15,7 +15,8 @@ URLPipeLoader::URLPipeLoader(
     std::unique_ptr<network::ResourceRequest> request,
     network::mojom::URLLoaderRequest loader,
     network::mojom::URLLoaderClientPtr client,
-    const net::NetworkTrafficAnnotationTag& annotation)
+    const net::NetworkTrafficAnnotationTag& annotation,
+    base::DictionaryValue upload_data)
     : binding_(this, std::move(loader)),
       client_(std::move(client)),
       weak_factory_(this) {
@@ -26,7 +27,7 @@ URLPipeLoader::URLPipeLoader(
   base::SequencedTaskRunnerHandle::Get()->PostTask(
       FROM_HERE,
       base::BindOnce(&URLPipeLoader::Start, weak_factory_.GetWeakPtr(), factory,
-                     std::move(request), annotation));
+                     std::move(request), annotation, std::move(upload_data)));
 }
 
 URLPipeLoader::~URLPipeLoader() = default;
@@ -34,10 +35,19 @@ URLPipeLoader::~URLPipeLoader() = default;
 void URLPipeLoader::Start(
     scoped_refptr<network::SharedURLLoaderFactory> factory,
     std::unique_ptr<network::ResourceRequest> request,
-    const net::NetworkTrafficAnnotationTag& annotation) {
+    const net::NetworkTrafficAnnotationTag& annotation,
+    base::DictionaryValue upload_data) {
   loader_ = network::SimpleURLLoader::Create(std::move(request), annotation);
   loader_->SetOnResponseStartedCallback(base::Bind(
       &URLPipeLoader::OnResponseStarted, weak_factory_.GetWeakPtr()));
+
+  // TODO(zcbenz): The old protocol API only supports string as upload data,
+  // we should seek to support more types in future.
+  std::string content_type, data;
+  if (upload_data.GetString("contentType", &content_type) &&
+      upload_data.GetString("data", &data))
+    loader_->AttachStringForUpload(data, content_type);
+
   loader_->DownloadAsStream(factory.get(), this);
 }
 
diff --git a/atom/browser/net/url_pipe_loader.h b/atom/browser/net/url_pipe_loader.h
index bf17783bc7..b41629b65d 100644
--- a/atom/browser/net/url_pipe_loader.h
+++ b/atom/browser/net/url_pipe_loader.h
@@ -35,14 +35,16 @@ class URLPipeLoader : public network::mojom::URLLoader,
                 std::unique_ptr<network::ResourceRequest> request,
                 network::mojom::URLLoaderRequest loader,
                 network::mojom::URLLoaderClientPtr client,
-                const net::NetworkTrafficAnnotationTag& annotation);
+                const net::NetworkTrafficAnnotationTag& annotation,
+                base::DictionaryValue upload_data);
 
  private:
   ~URLPipeLoader() override;
 
   void Start(scoped_refptr<network::SharedURLLoaderFactory> factory,
              std::unique_ptr<network::ResourceRequest> request,
-             const net::NetworkTrafficAnnotationTag& annotation);
+             const net::NetworkTrafficAnnotationTag& annotation,
+             base::DictionaryValue upload_data);
   void NotifyComplete(int result);
   void OnResponseStarted(const GURL& final_url,
                          const network::ResourceResponseHead& response_head);
diff --git a/atom/common/native_mate_converters/net_converter.cc b/atom/common/native_mate_converters/net_converter.cc
index 27859c6e83..aed3d9c102 100644
--- a/atom/common/native_mate_converters/net_converter.cc
+++ b/atom/common/native_mate_converters/net_converter.cc
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "atom/common/native_mate_converters/gurl_converter.h"
+#include "atom/common/native_mate_converters/string16_converter.h"
 #include "atom/common/native_mate_converters/value_converter.h"
 #include "atom/common/node_includes.h"
 #include "base/strings/string_number_conversions.h"
@@ -237,7 +238,33 @@ v8::Local<v8::Value> Converter<network::ResourceRequest>::ToV8(
   for (net::HttpRequestHeaders::Iterator it(val.headers); it.GetNext();)
     headers.Set(it.name(), it.value());
   dict.Set("headers", headers);
-  // FIXME(zcbenz): Figure out how to support uploadData.
+  if (val.request_body) {
+    const auto& elements = *val.request_body->elements();
+    v8::Local<v8::Array> arr = v8::Array::New(isolate, elements.size());
+    for (size_t i = 0; i < elements.size(); ++i) {
+      const auto& element = elements[i];
+      mate::Dictionary upload_data(isolate, v8::Object::New(isolate));
+      switch (element.type()) {
+        case network::mojom::DataElementType::kFile:
+          upload_data.Set("file", element.path().value());
+          break;
+        case network::mojom::DataElementType::kBytes:
+          upload_data.Set("bytes", node::Buffer::Copy(isolate, element.bytes(),
+                                                      element.length())
+                                       .ToLocalChecked());
+          break;
+        case network::mojom::DataElementType::kBlob:
+          upload_data.Set("blobUUID", element.blob_uuid());
+          break;
+        default:
+          NOTREACHED() << "Found unsupported data element";
+      }
+      arr->Set(isolate->GetCurrentContext(), static_cast<uint32_t>(i),
+               upload_data.GetHandle())
+          .Check();
+    }
+    dict.Set("uploadData", arr);
+  }
   return dict.GetHandle();
 }