diff --git a/components/embedder_traits/lib.rs b/components/embedder_traits/lib.rs
index 9d4e56dd297..d8773318e35 100644
--- a/components/embedder_traits/lib.rs
+++ b/components/embedder_traits/lib.rs
@@ -240,6 +240,24 @@ pub enum MediaSessionPlaybackState {
     Paused,
 }
 
+/// https://w3c.github.io/mediasession/#dictdef-mediapositionstate
+#[derive(Clone, Debug, Deserialize, Serialize)]
+pub struct MediaPositionState {
+    pub duration: Option<f64>,
+    pub playback_rate: Option<f64>,
+    pub position: Option<f64>,
+}
+
+impl MediaPositionState {
+    pub fn new(duration: f64, playback_rate: f64, position: f64) -> Self {
+        Self {
+            duration,
+            playback_rate,
+            position,
+        }
+    }
+}
+
 /// Type of events sent from script to the embedder about the media session.
 #[derive(Clone, Debug, Deserialize, Serialize)]
 pub enum MediaSessionEvent {
@@ -247,4 +265,6 @@ pub enum MediaSessionEvent {
     SetMetadata(MediaMetadata),
     /// Indicates that the playback state has changed.
     PlaybackStateChange(MediaSessionPlaybackState),
+    /// Indicates that the position state is set.
+    SetPositionState(MediaPositionState),
 }
diff --git a/components/script/dom/htmlmediaelement.rs b/components/script/dom/htmlmediaelement.rs
index 0780a81e2e6..cf179aee439 100644
--- a/components/script/dom/htmlmediaelement.rs
+++ b/components/script/dom/htmlmediaelement.rs
@@ -67,7 +67,7 @@ use crate::script_thread::ScriptThread;
 use crate::task_source::TaskSource;
 use dom_struct::dom_struct;
 use embedder_traits::resources::{self, Resource as EmbedderResource};
-use embedder_traits::{MediaSessionEvent, MediaSessionPlaybackState};
+use embedder_traits::{MediaPositionState, MediaSessionEvent, MediaSessionPlaybackState};
 use euclid::default::Size2D;
 use headers::{ContentLength, ContentRange, HeaderMapExt};
 use html5ever::{LocalName, Prefix};
@@ -1780,6 +1780,15 @@ impl HTMLMediaElement {
                     .add(self.playback_position.get(), position);
                 self.playback_position.set(position);
                 self.time_marches_on();
+                let media_position_state =
+                    MediaPositionState::new(self.duration.get(), self.playbackRate.get(), position);
+                debug!(
+                    "Sending media session event set position state {:?}",
+                    media_position_state
+                );
+                self.send_media_session_event(MediaSessionEvent::SetPositionState(
+                    media_position_state,
+                ));
             },
             PlayerEvent::SeekData(p, ref seek_lock) => {
                 self.fetch_request(Some(p), Some(seek_lock.clone()));