diff --git a/openstack/blockstorage/v2/extensions/volumeactions/requests.go b/openstack/blockstorage/v2/extensions/volumeactions/requests.go
index 05a76f7..d2a2c79 100644
--- a/openstack/blockstorage/v2/extensions/volumeactions/requests.go
+++ b/openstack/blockstorage/v2/extensions/volumeactions/requests.go
@@ -172,3 +172,36 @@
 	})
 	return
 }
+
+// ExtendSizeOptsBuilder allows extensions to add additional parameters to the
+// ExtendSize request.
+type ExtendSizeOptsBuilder interface {
+	ToVolumeExtendSizeMap() (map[string]interface{}, error)
+}
+
+// ExtendSizeOpts contain options for extending the size of an existing Volume. This object is passed
+// to the volumes.ExtendSize function.
+type ExtendSizeOpts struct {
+	// NewSize is the new size of the volume, in GB
+	NewSize int `json:"new_size" required:"true"`
+}
+
+// ToVolumeExtendSizeMap assembles a request body based on the contents of an
+// ExtendSizeOpts.
+func (opts ExtendSizeOpts) ToVolumeExtendSizeMap() (map[string]interface{}, error) {
+	return gophercloud.BuildRequestBody(opts, "os-extend")
+}
+
+// ExtendSize will extend the size of the volume based on the provided information.
+// This operation does not return a response body.
+func ExtendSize(client *gophercloud.ServiceClient, id string, opts ExtendSizeOptsBuilder) (r ExtendSizeResult) {
+	b, err := opts.ToVolumeExtendSizeMap()
+	if err != nil {
+		r.Err = err
+		return
+	}
+	_, r.Err = client.Post(extendSizeURL(client, id), b, &r.Body, &gophercloud.RequestOpts{
+		OkCodes: []int{202},
+	})
+	return
+}
diff --git a/openstack/blockstorage/v2/extensions/volumeactions/results.go b/openstack/blockstorage/v2/extensions/volumeactions/results.go
index 9bf6a7b..f9e8120 100644
--- a/openstack/blockstorage/v2/extensions/volumeactions/results.go
+++ b/openstack/blockstorage/v2/extensions/volumeactions/results.go
@@ -44,3 +44,8 @@
 type InitializeConnectionResult struct {
 	commonResult
 }
+
+// ExtendSizeResult contains the response body and error from an ExtendSize request.
+type ExtendSizeResult struct {
+	gophercloud.ErrResult
+}
diff --git a/openstack/blockstorage/v2/extensions/volumeactions/testing/fixtures.go b/openstack/blockstorage/v2/extensions/volumeactions/testing/fixtures.go
index da661a6..34df070 100644
--- a/openstack/blockstorage/v2/extensions/volumeactions/testing/fixtures.go
+++ b/openstack/blockstorage/v2/extensions/volumeactions/testing/fixtures.go
@@ -181,3 +181,26 @@
 			fmt.Fprintf(w, `{}`)
 		})
 }
+
+func MockExtendSizeResponse(t *testing.T) {
+	th.Mux.HandleFunc("/volumes/cd281d77-8217-4830-be95-9528227c105c/action",
+		func(w http.ResponseWriter, r *http.Request) {
+			th.TestMethod(t, r, "POST")
+			th.TestHeader(t, r, "X-Auth-Token", fake.TokenID)
+			th.TestHeader(t, r, "Content-Type", "application/json")
+			th.TestHeader(t, r, "Accept", "application/json")
+			th.TestJSONRequest(t, r, `
+{
+    "os-extend":
+    {
+        "new_size": 3
+    }
+}
+          `)
+
+			w.Header().Add("Content-Type", "application/json")
+			w.WriteHeader(http.StatusAccepted)
+
+			fmt.Fprintf(w, `{}`)
+		})
+}
diff --git a/openstack/blockstorage/v2/extensions/volumeactions/testing/requests_test.go b/openstack/blockstorage/v2/extensions/volumeactions/testing/requests_test.go
index dac4e01..38a5bd2 100644
--- a/openstack/blockstorage/v2/extensions/volumeactions/testing/requests_test.go
+++ b/openstack/blockstorage/v2/extensions/volumeactions/testing/requests_test.go
@@ -89,3 +89,17 @@
 	err := volumeactions.TerminateConnection(client.ServiceClient(), "cd281d77-8217-4830-be95-9528227c105c", options).ExtractErr()
 	th.AssertNoErr(t, err)
 }
+
+func TestExtendSize(t *testing.T) {
+	th.SetupHTTP()
+	defer th.TeardownHTTP()
+
+	MockExtendSizeResponse(t)
+
+	options := &volumeactions.ExtendSizeOpts{
+		NewSize: 3,
+	}
+
+	err := volumeactions.ExtendSize(client.ServiceClient(), "cd281d77-8217-4830-be95-9528227c105c", options).ExtractErr()
+	th.AssertNoErr(t, err)
+}
diff --git a/openstack/blockstorage/v2/extensions/volumeactions/urls.go b/openstack/blockstorage/v2/extensions/volumeactions/urls.go
index 4ddcca0..a61ee7d 100644
--- a/openstack/blockstorage/v2/extensions/volumeactions/urls.go
+++ b/openstack/blockstorage/v2/extensions/volumeactions/urls.go
@@ -25,3 +25,7 @@
 func teminateConnectionURL(c *gophercloud.ServiceClient, id string) string {
 	return attachURL(c, id)
 }
+
+func extendSizeURL(c *gophercloud.ServiceClient, id string) string {
+	return attachURL(c, id)
+}