diff --git a/patches/chromium/.patches b/patches/chromium/.patches
index 0ab5f7115d987..fedcf08c646ef 100644
--- a/patches/chromium/.patches
+++ b/patches/chromium/.patches
@@ -196,3 +196,4 @@ feat_brightsign_add_mouse_wheel_scroll_to_evdev.patch
 gin_cap_v8_coderange_to_64mb_on_low-memory_systems.patch
 brightsign_fix_black_transparent_hole_being_shown_before_video.patch
 feat_map_krolealwaysontop_z-order_level_to_always-on-top_surface.patch
+feat_brightsign_add_setattribute_and_setsyncparams_os-21421.patch
diff --git a/patches/chromium/feat_brightsign_add_setattribute_and_setsyncparams_os-21421.patch b/patches/chromium/feat_brightsign_add_setattribute_and_setsyncparams_os-21421.patch
new file mode 100644
index 0000000000000..fa739dbdc5740
--- /dev/null
+++ b/patches/chromium/feat_brightsign_add_setattribute_and_setsyncparams_os-21421.patch
@@ -0,0 +1,53 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Tariq Bashir <tbashir@brightsign.biz>
+Date: Wed, 8 Jul 2026 09:16:30 +0100
+Subject: feat: Brightsign add SetAttribute and SetSyncParams OS-21421
+
+Methods SetAttribute and SetSyncParams were in WebMediaPlayerBrightsign
+but commented out, this patch adds the implementation of these methods.
+
+diff --git a/third_party/blink/renderer/platform/media/brightsign/web_media_player_brightsign.cc b/third_party/blink/renderer/platform/media/brightsign/web_media_player_brightsign.cc
+index fcb37533003158c741f1e2fa31da1f0760d8bc41..4dd2c1cd5c9ed72663d79ae95e3f24b79682ca33 100644
+--- a/third_party/blink/renderer/platform/media/brightsign/web_media_player_brightsign.cc
++++ b/third_party/blink/renderer/platform/media/brightsign/web_media_player_brightsign.cc
+@@ -820,20 +820,20 @@ bool WebMediaPlayerBrightsign::HasReadableVideoFrame() const {
+ 
+ void OnReleaseTexture(gpu::Mailbox mbox) {}
+ 
+-/*
++
+ void WebMediaPlayerBrightsign::SetAttribute(const std::string& name,
+                                             const std::string& value) {
+   VLOG(1) << __func__;
+-  vid_player_->SetAttribute(name, value);
++  vid_player_set_attribute(vid_player_, name.c_str(), value.c_str());
+ }
+ 
+ void WebMediaPlayerBrightsign::SetSyncParams(const std::string& domain,
+                                              const std::string& id,
+                                              const std::string& timestamp) {
+   VLOG(1) << __func__;
+-  vid_player_->SetSyncParams(domain, id, timestamp);
++  vid_player_set_sync_params(vid_player_, domain.c_str(), id.c_str(), timestamp.c_str());
+ }
+-*/
++
+ 
+ void WebMediaPlayerBrightsign::SetNetworkState(
+     WebMediaPlayer::NetworkState state) {
+diff --git a/third_party/blink/renderer/platform/media/brightsign/web_media_player_brightsign.h b/third_party/blink/renderer/platform/media/brightsign/web_media_player_brightsign.h
+index 695578bd44f101d22008d7cdc168436ad3a0ab80..e257f0c57070825b7ae430992ef7abeec86fc1aa 100644
+--- a/third_party/blink/renderer/platform/media/brightsign/web_media_player_brightsign.h
++++ b/third_party/blink/renderer/platform/media/brightsign/web_media_player_brightsign.h
+@@ -182,9 +182,8 @@ class WebMediaPlayerBrightsign
+   void SubtitleUpdatedCallback(const std::vector< std::map<std::string, std::string> >& text_tracks);
+   void TextureMailboxReadyCallback(const VidPlayerMailboxData& mbox);
+ 
+-  // void SetAttribute(const std::string& name, const std::string& value)
+-  // override; void SetSyncParams(const std::string& domain, const std::string&
+-  // id, const std::string& timestamp) override;
++  void SetAttribute(const std::string& name, const std::string& value) override;
++  void SetSyncParams(const std::string& domain, const std::string& id, const std::string& timestamp) override;
+ 
+   void OnProgress();
+   void OnEncryptedMediaInitData(media::EmeInitDataType init_data_type,