diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4b47918f..8e460d27 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,7 @@
 # Unreleased
 
+- [added] `messaging.ApsAlert` type now supports subtitle in its payload.
+
 # v3.4.0
 
 - [added] `firebase.App` now provides a new `DatabaseWithURL()` function
diff --git a/messaging/messaging.go b/messaging/messaging.go
index 5d18dc93..91bd7838 100644
--- a/messaging/messaging.go
+++ b/messaging/messaging.go
@@ -399,14 +399,17 @@ func (a *Aps) MarshalJSON() ([]byte, error) {
 // See https://developer.apple.com/library/content/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/PayloadKeyReference.html
 // for supported fields.
 type ApsAlert struct {
-	Title        string   `json:"title,omitempty"` // if specified, overrides the Title field of the Notification type
-	Body         string   `json:"body,omitempty"`  // if specified, overrides the Body field of the Notification type
-	LocKey       string   `json:"loc-key,omitempty"`
-	LocArgs      []string `json:"loc-args,omitempty"`
-	TitleLocKey  string   `json:"title-loc-key,omitempty"`
-	TitleLocArgs []string `json:"title-loc-args,omitempty"`
-	ActionLocKey string   `json:"action-loc-key,omitempty"`
-	LaunchImage  string   `json:"launch-image,omitempty"`
+	Title           string   `json:"title,omitempty"` // if specified, overrides the Title field of the Notification type
+	SubTitle        string   `json:"subtitle,omitempty"`
+	Body            string   `json:"body,omitempty"` // if specified, overrides the Body field of the Notification type
+	LocKey          string   `json:"loc-key,omitempty"`
+	LocArgs         []string `json:"loc-args,omitempty"`
+	TitleLocKey     string   `json:"title-loc-key,omitempty"`
+	TitleLocArgs    []string `json:"title-loc-args,omitempty"`
+	SubTitleLocKey  string   `json:"subtitle-loc-key,omitempty"`
+	SubTitleLocArgs []string `json:"subtitle-loc-args,omitempty"`
+	ActionLocKey    string   `json:"action-loc-key,omitempty"`
+	LaunchImage     string   `json:"launch-image,omitempty"`
 }
 
 // ErrorInfo is a topic management error.
diff --git a/messaging/messaging_test.go b/messaging/messaging_test.go
index 55a6f4cd..bc8382ff 100644
--- a/messaging/messaging_test.go
+++ b/messaging/messaging_test.go
@@ -370,14 +370,17 @@ var validMessages = []struct {
 				Payload: &APNSPayload{
 					Aps: &Aps{
 						Alert: &ApsAlert{
-							Title:        "t",
-							Body:         "b",
-							TitleLocKey:  "tlk",
-							TitleLocArgs: []string{"t1", "t2"},
-							LocKey:       "blk",
-							LocArgs:      []string{"b1", "b2"},
-							ActionLocKey: "alk",
-							LaunchImage:  "li",
+							Title:           "t",
+							SubTitle:        "st",
+							Body:            "b",
+							TitleLocKey:     "tlk",
+							TitleLocArgs:    []string{"t1", "t2"},
+							SubTitleLocKey:  "stlk",
+							SubTitleLocArgs: []string{"t1", "t2"},
+							LocKey:          "blk",
+							LocArgs:         []string{"b1", "b2"},
+							ActionLocKey:    "alk",
+							LaunchImage:     "li",
 						},
 					},
 				},
@@ -389,14 +392,17 @@ var validMessages = []struct {
 				"payload": map[string]interface{}{
 					"aps": map[string]interface{}{
 						"alert": map[string]interface{}{
-							"title":          "t",
-							"body":           "b",
-							"title-loc-key":  "tlk",
-							"title-loc-args": []interface{}{"t1", "t2"},
-							"loc-key":        "blk",
-							"loc-args":       []interface{}{"b1", "b2"},
-							"action-loc-key": "alk",
-							"launch-image":   "li",
+							"title":             "t",
+							"subtitle":          "st",
+							"body":              "b",
+							"title-loc-key":     "tlk",
+							"title-loc-args":    []interface{}{"t1", "t2"},
+							"subtitle-loc-key":  "stlk",
+							"subtitle-loc-args": []interface{}{"t1", "t2"},
+							"loc-key":           "blk",
+							"loc-args":          []interface{}{"b1", "b2"},
+							"action-loc-key":    "alk",
+							"launch-image":      "li",
 						},
 					},
 				},
@@ -557,6 +563,22 @@ var invalidMessages = []struct {
 		},
 		want: "titleLocKey is required when specifying titleLocArgs",
 	},
+	{
+		name: "InvalidAPNSSubTitleLocArgs",
+		req: &Message{
+			APNS: &APNSConfig{
+				Payload: &APNSPayload{
+					Aps: &Aps{
+						Alert: &ApsAlert{
+							SubTitleLocArgs: []string{"a1"},
+						},
+					},
+				},
+			},
+			Topic: "topic",
+		},
+		want: "subtitleLocKey is required when specifying subtitleLocArgs",
+	},
 	{
 		name: "InvalidAPNSLocArgs",
 		req: &Message{
diff --git a/messaging/messaging_utils.go b/messaging/messaging_utils.go
index 9c7a99b7..d34aba79 100644
--- a/messaging/messaging_utils.go
+++ b/messaging/messaging_utils.go
@@ -126,6 +126,9 @@ func validateApsAlert(alert *ApsAlert) error {
 	if len(alert.TitleLocArgs) > 0 && alert.TitleLocKey == "" {
 		return fmt.Errorf("titleLocKey is required when specifying titleLocArgs")
 	}
+	if len(alert.SubTitleLocArgs) > 0 && alert.SubTitleLocKey == "" {
+		return fmt.Errorf("subtitleLocKey is required when specifying subtitleLocArgs")
+	}
 	if len(alert.LocArgs) > 0 && alert.LocKey == "" {
 		return fmt.Errorf("locKey is required when specifying locArgs")
 	}