diff --git a/pkg/cmd/release/create/create.go b/pkg/cmd/release/create/create.go
index 0e492dcc6..afb30e829 100644
--- a/pkg/cmd/release/create/create.go
+++ b/pkg/cmd/release/create/create.go
@@ -89,10 +89,6 @@ func createRun(opts *CreateOptions) error {
 		return api.HandleHTTPError(resp)
 	}
 
-	if resp.StatusCode == http.StatusNoContent {
-		return nil
-	}
-
 	b, err := ioutil.ReadAll(resp.Body)
 	if err != nil {
 		return err
diff --git a/pkg/cmd/release/release.go b/pkg/cmd/release/release.go
index de2613acd..dedf38afe 100644
--- a/pkg/cmd/release/release.go
+++ b/pkg/cmd/release/release.go
@@ -3,6 +3,7 @@ package release
 import (
 	cmdCreate "github.com/cli/cli/pkg/cmd/release/create"
 	cmdList "github.com/cli/cli/pkg/cmd/release/list"
+	cmdUpload "github.com/cli/cli/pkg/cmd/release/upload"
 	cmdView "github.com/cli/cli/pkg/cmd/release/view"
 	"github.com/cli/cli/pkg/cmdutil"
 	"github.com/spf13/cobra"
@@ -22,6 +23,7 @@ func NewCmdRelease(f *cmdutil.Factory) *cobra.Command {
 	cmd.AddCommand(cmdCreate.NewCmdCreate(f, nil))
 	cmd.AddCommand(cmdList.NewCmdList(f, nil))
 	cmd.AddCommand(cmdView.NewCmdView(f, nil))
+	cmd.AddCommand(cmdUpload.NewCmdUpload(f, nil))
 
 	return cmd
 }
diff --git a/pkg/cmd/release/upload/http.go b/pkg/cmd/release/upload/http.go
new file mode 100644
index 000000000..8b66c690d
--- /dev/null
+++ b/pkg/cmd/release/upload/http.go
@@ -0,0 +1,121 @@
+package upload
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+
+	"github.com/cli/cli/api"
+	"github.com/cli/cli/internal/ghinstance"
+	"github.com/cli/cli/internal/ghrepo"
+)
+
+type Release struct {
+	UploadURL string `json:"upload_url"`
+	Assets    []ReleaseAsset
+}
+
+type ReleaseAsset struct {
+	Name  string
+	State string
+	URL   string
+}
+
+func fetchRelease(httpClient *http.Client, baseRepo ghrepo.Interface, tagName string) (*Release, error) {
+	path := fmt.Sprintf("repos/%s/%s/releases/tags/%s", baseRepo.RepoOwner(), baseRepo.RepoName(), tagName)
+	url := ghinstance.RESTPrefix(baseRepo.RepoHost()) + path
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	req.Header.Set("Content-Type", "application/json; charset=utf-8")
+
+	resp, err := httpClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	success := resp.StatusCode >= 200 && resp.StatusCode < 300
+	if !success {
+		return nil, api.HandleHTTPError(resp)
+	}
+
+	b, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var release Release
+	err = json.Unmarshal(b, &release)
+	if err != nil {
+		return nil, err
+	}
+
+	return &release, nil
+}
+
+func uploadAsset(httpClient *http.Client, uploadURL string, asset AssetForUpload) (*ReleaseAsset, error) {
+	u, err := url.Parse(uploadURL)
+	if err != nil {
+		return nil, err
+	}
+	params := u.Query()
+	params.Set("name", asset.Name)
+	params.Set("label", asset.Label)
+	u.RawQuery = params.Encode()
+
+	req, err := http.NewRequest("POST", u.String(), asset.Data)
+	if err != nil {
+		return nil, err
+	}
+	req.ContentLength = asset.Size
+	req.Header.Set("Content-Type", asset.MIMEType)
+
+	resp, err := httpClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	success := resp.StatusCode >= 200 && resp.StatusCode < 300
+	if !success {
+		return nil, api.HandleHTTPError(resp)
+	}
+
+	b, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var newAsset ReleaseAsset
+	err = json.Unmarshal(b, &newAsset)
+	if err != nil {
+		return nil, err
+	}
+
+	return &newAsset, nil
+}
+
+func deleteAsset(httpClient *http.Client, assetURL string) error {
+	req, err := http.NewRequest("DELETE", assetURL, nil)
+	if err != nil {
+		return err
+	}
+
+	resp, err := httpClient.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	success := resp.StatusCode >= 200 && resp.StatusCode < 300
+	if !success {
+		return api.HandleHTTPError(resp)
+	}
+
+	return nil
+}
diff --git a/pkg/cmd/release/upload/upload.go b/pkg/cmd/release/upload/upload.go
new file mode 100644
index 000000000..beefb55d5
--- /dev/null
+++ b/pkg/cmd/release/upload/upload.go
@@ -0,0 +1,186 @@
+package upload
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/cli/cli/internal/ghrepo"
+	"github.com/cli/cli/pkg/cmdutil"
+	"github.com/cli/cli/pkg/iostreams"
+	"github.com/spf13/cobra"
+)
+
+type UploadOptions struct {
+	HttpClient func() (*http.Client, error)
+	IO         *iostreams.IOStreams
+	BaseRepo   func() (ghrepo.Interface, error)
+
+	TagName string
+	Assets  []*AssetForUpload
+
+	// maximum number of simultaneous uploads
+	Concurrency       int
+	OverwriteExisting bool
+}
+
+type AssetForUpload struct {
+	Name  string
+	Label string
+
+	Data     io.ReadCloser
+	Size     int64
+	MIMEType string
+
+	ExistingURL string
+}
+
+func NewCmdUpload(f *cmdutil.Factory, runF func(*UploadOptions) error) *cobra.Command {
+	opts := &UploadOptions{
+		IO:         f.IOStreams,
+		HttpClient: f.HttpClient,
+	}
+
+	cmd := &cobra.Command{
+		Use:   "upload <tag> <files>...",
+		Short: "Upload assets to a release",
+		Args:  cobra.MinimumNArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			// support `-R, --repo` override
+			opts.BaseRepo = f.BaseRepo
+
+			opts.TagName = args[0]
+
+			var err error
+			opts.Assets, err = assetsFromArgs(args[1:])
+			if err != nil {
+				return err
+			}
+
+			opts.Concurrency = 5
+
+			if runF != nil {
+				return runF(opts)
+			}
+			return uploadRun(opts)
+		},
+	}
+
+	cmd.Flags().BoolVar(&opts.OverwriteExisting, "clobber", false, "Overwrite existing assets of the same name")
+
+	return cmd
+}
+
+func assetsFromArgs(args []string) (assets []*AssetForUpload, err error) {
+	for _, fn := range args {
+		var f *os.File
+		var fi os.FileInfo
+
+		f, err = os.Open(fn)
+		if err != nil {
+			return
+		}
+		fi, err = f.Stat()
+		if err != nil {
+			return
+		}
+
+		assets = append(assets, &AssetForUpload{
+			Data:  f,
+			Size:  fi.Size(),
+			Name:  filepath.Base(fn),
+			Label: "",
+			// TODO: infer content type from file extension
+			MIMEType: "application/octet-stream",
+		})
+	}
+	return
+}
+
+func uploadRun(opts *UploadOptions) error {
+	httpClient, err := opts.HttpClient()
+	if err != nil {
+		return err
+	}
+
+	baseRepo, err := opts.BaseRepo()
+	if err != nil {
+		return err
+	}
+
+	release, err := fetchRelease(httpClient, baseRepo, opts.TagName)
+	if err != nil {
+		return err
+	}
+
+	uploadURL := release.UploadURL
+	if idx := strings.IndexRune(uploadURL, '{'); idx > 0 {
+		uploadURL = uploadURL[:idx]
+	}
+
+	var existingNames []string
+	for _, a := range opts.Assets {
+		for _, ea := range release.Assets {
+			if ea.Name == a.Name {
+				a.ExistingURL = ea.URL
+				existingNames = append(existingNames, ea.Name)
+				break
+			}
+		}
+	}
+
+	if len(existingNames) > 0 && !opts.OverwriteExisting {
+		return fmt.Errorf("asset under the same name already exists: %v", existingNames)
+	}
+
+	opts.IO.StartProgressIndicator()
+	err = concurrentUpload(httpClient, uploadURL, opts.Concurrency, opts.Assets)
+	opts.IO.EndProgressIndicator()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func concurrentUpload(httpClient *http.Client, uploadURL string, numWorkers int, assets []*AssetForUpload) error {
+	jobs := make(chan AssetForUpload, len(assets))
+	results := make(chan error, len(assets))
+
+	for w := 1; w <= numWorkers; w++ {
+		go func() {
+			for a := range jobs {
+				results <- uploadWithDelete(httpClient, uploadURL, a)
+			}
+		}()
+	}
+
+	for _, a := range assets {
+		jobs <- *a
+	}
+	close(jobs)
+
+	var uploadError error
+	for i := 0; i < len(assets); i++ {
+		if err := <-results; err != nil {
+			uploadError = err
+		}
+	}
+	return uploadError
+}
+
+func uploadWithDelete(httpClient *http.Client, uploadURL string, a AssetForUpload) error {
+	if a.ExistingURL != "" {
+		err := deleteAsset(httpClient, a.ExistingURL)
+		if err != nil {
+			return err
+		}
+	}
+
+	defer a.Data.Close()
+	_, err := uploadAsset(httpClient, uploadURL, a)
+	return err
+}
diff --git a/pkg/iostreams/iostreams.go b/pkg/iostreams/iostreams.go
index cf69ecd8c..25d447371 100644
--- a/pkg/iostreams/iostreams.go
+++ b/pkg/iostreams/iostreams.go
@@ -9,7 +9,9 @@ import (
 	"os/exec"
 	"strconv"
 	"strings"
+	"time"
 
+	"github.com/briandowns/spinner"
 	"github.com/mattn/go-colorable"
 	"github.com/mattn/go-isatty"
 	"golang.org/x/crypto/ssh/terminal"
@@ -22,6 +24,9 @@ type IOStreams struct {
 
 	colorEnabled bool
 
+	progressIndicatorEnabled bool
+	progressIndicator        *spinner.Spinner
+
 	stdinTTYOverride  bool
 	stdinIsTTY        bool
 	stdoutTTYOverride bool
@@ -79,6 +84,23 @@ func (s *IOStreams) IsStderrTTY() bool {
 	return false
 }
 
+func (s *IOStreams) StartProgressIndicator() {
+	if !s.progressIndicatorEnabled {
+		return
+	}
+	sp := spinner.New(spinner.CharSets[11], 400*time.Millisecond, spinner.WithWriter(s.ErrOut))
+	sp.Start()
+	s.progressIndicator = sp
+}
+
+func (s *IOStreams) EndProgressIndicator() {
+	if s.progressIndicator == nil {
+		return
+	}
+	s.progressIndicator.Stop()
+	s.progressIndicator = nil
+}
+
 func (s *IOStreams) TerminalWidth() int {
 	defaultWidth := 80
 	if s.stdoutTTYOverride {
@@ -104,18 +126,30 @@ func (s *IOStreams) TerminalWidth() int {
 
 func System() *IOStreams {
 	var out io.Writer = os.Stdout
+	stdoutIsTTY := isTerminal(os.Stdout)
+	stderrIsTTY := isTerminal(os.Stderr)
+
 	var colorEnabled bool
-	if os.Getenv("NO_COLOR") == "" && isTerminal(os.Stdout) {
+	if os.Getenv("NO_COLOR") == "" && stdoutIsTTY {
 		out = colorable.NewColorable(os.Stdout)
 		colorEnabled = true
 	}
 
-	return &IOStreams{
+	io := &IOStreams{
 		In:           os.Stdin,
 		Out:          out,
 		ErrOut:       os.Stderr,
 		colorEnabled: colorEnabled,
 	}
+
+	if stdoutIsTTY && stderrIsTTY {
+		io.progressIndicatorEnabled = true
+	}
+
+	// prevent duplicate isTerminal queries now that we know the answer
+	io.SetStdoutTTY(stdoutIsTTY)
+	io.SetStderrTTY(stderrIsTTY)
+	return io
 }
 
 func Test() (*IOStreams, *bytes.Buffer, *bytes.Buffer, *bytes.Buffer) {