diff --git a/client/client.go b/client/client.go
index 74d4b0fd..1cdc0166 100644
--- a/client/client.go
+++ b/client/client.go
@@ -79,6 +79,27 @@ type CSAPI struct {
 	txnID int64
 }
 
+// CreateMedia creates an MXC URI for asynchronous media uploads.
+func (c *CSAPI) CreateMedia(t TestLike) string {
+	t.Helper()
+	res := c.MustDo(t, "POST", []string{"_matrix", "media", "v1", "create"})
+	body := ParseJSON(t, res)
+	return GetJSONFieldStr(t, body, "content_uri")
+}
+
+// UploadMediaAsync uploads the provided content to the given server and media ID. Fails the test on error.
+func (c *CSAPI) UploadMediaAsync(t TestLike, serverName, mediaID string, fileBody []byte, fileName string, contentType string) {
+	t.Helper()
+	query := url.Values{}
+	if fileName != "" {
+		query.Set("filename", fileName)
+	}
+	c.MustDo(
+		t, "PUT", []string{"_matrix", "media", "v3", "upload", serverName, mediaID},
+		WithRawBody(fileBody), WithContentType(contentType), WithQueries(query),
+	)
+}
+
 // UploadContent uploads the provided content with an optional file name. Fails the test on error. Returns the MXC URI.
 func (c *CSAPI) UploadContent(t TestLike, fileBody []byte, fileName string, contentType string) string {
 	t.Helper()
diff --git a/tests/csapi/media_async_uploads_test.go b/tests/csapi/media_async_uploads_test.go
new file mode 100644
index 00000000..901caa45
--- /dev/null
+++ b/tests/csapi/media_async_uploads_test.go
@@ -0,0 +1,73 @@
+package csapi_tests
+
+import (
+	"bytes"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/matrix-org/complement"
+	"github.com/matrix-org/complement/client"
+	"github.com/matrix-org/complement/helpers"
+	"github.com/matrix-org/complement/internal/data"
+	"github.com/matrix-org/complement/match"
+	"github.com/matrix-org/complement/must"
+	"github.com/matrix-org/complement/runtime"
+)
+
+func TestAsyncUpload(t *testing.T) {
+	runtime.SkipIf(t, runtime.Dendrite) // Dendrite doesn't support async uploads
+
+	deployment := complement.Deploy(t, 1)
+	defer deployment.Destroy(t)
+
+	alice := deployment.Register(t, "hs1", helpers.RegistrationOpts{})
+
+	var mxcURI, mediaID string
+	t.Run("Create media", func(t *testing.T) {
+		mxcURI = alice.CreateMedia(t)
+		parts := strings.Split(mxcURI, "/")
+		mediaID = parts[len(parts)-1]
+	})
+
+	origin, mediaID := client.SplitMxc(mxcURI)
+
+	t.Run("Not yet uploaded", func(t *testing.T) {
+		// Check that the media is not yet uploaded
+		res := alice.Do(t, "GET", []string{"_matrix", "media", "v3", "download", origin, mediaID})
+		must.MatchResponse(t, res, match.HTTPResponse{
+			StatusCode: http.StatusGatewayTimeout,
+			JSON: []match.JSON{
+				match.JSONKeyEqual("errcode", "M_NOT_YET_UPLOADED"),
+				match.JSONKeyEqual("error", "Media has not been uploaded yet"),
+			},
+		})
+	})
+
+	wantContentType := "image/png"
+
+	t.Run("Upload media", func(t *testing.T) {
+		alice.UploadMediaAsync(t, origin, mediaID, data.MatrixPng, "test.png", wantContentType)
+	})
+
+	t.Run("Cannot upload to a media ID that has already been uploaded to", func(t *testing.T) {
+		res := alice.Do(t, "PUT", []string{"_matrix", "media", "v3", "upload", origin, mediaID})
+		must.MatchResponse(t, res, match.HTTPResponse{
+			StatusCode: http.StatusConflict,
+			JSON: []match.JSON{
+				match.JSONKeyEqual("errcode", "M_CANNOT_OVERWRITE_MEDIA"),
+				match.JSONKeyEqual("error", "Media ID already has content"),
+			},
+		})
+	})
+
+	t.Run("Download media", func(t *testing.T) {
+		content, contentType := alice.DownloadContent(t, mxcURI)
+		if !bytes.Equal(data.MatrixPng, content) {
+			t.Fatalf("uploaded and downloaded content doesn't match: want %v\ngot\n%v", data.MatrixPng, content)
+		}
+		if contentType != wantContentType {
+			t.Fatalf("expected contentType to be %s, got %s", wantContentType, contentType)
+		}
+	})
+}