diff --git a/app/assets/stylesheets/notifications.css b/app/assets/stylesheets/notifications.css
index 878eb25c5..b50e35a2c 100644
--- a/app/assets/stylesheets/notifications.css
+++ b/app/assets/stylesheets/notifications.css
@@ -40,6 +40,13 @@
     }
   }
 
+  /* Grouped notifications
+  /* ------------------------------------------------------------------------ */
+
+  .notification--grouped {
+    border: 3px solid red;
+  }
+
   /* Read items
   /* ------------------------------------------------------------------------ */
 
diff --git a/app/helpers/notifications_helper.rb b/app/helpers/notifications_helper.rb
index c557624be..69eab11a6 100644
--- a/app/helpers/notifications_helper.rb
+++ b/app/helpers/notifications_helper.rb
@@ -20,7 +20,10 @@ module NotificationsHelper
   end
 
   def notification_tag(notification, &)
-    tag.div id: dom_id(notification), class: "tray__item tray__item--notification", data: { navigable_list_target: "item" } do
+    tag.div id: dom_id(notification), class: "tray__item tray__item--notification", data: {
+      navigable_list_target: "item",
+      notifications_tray_target: "notification",
+      card_id: notification.card.id, timestamp: notification.created_at.to_i } do
       concat(
         link_to(notification,
           class: [ "card card--notification", { "card--closed": notification.card.closed? }, { "unread": !notification.read? } ],
diff --git a/app/javascript/controllers/notifications_tray_controller.js b/app/javascript/controllers/notifications_tray_controller.js
new file mode 100644
index 000000000..b356c4b20
--- /dev/null
+++ b/app/javascript/controllers/notifications_tray_controller.js
@@ -0,0 +1,57 @@
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  static targets = [ "notification", "hiddenNotifications" ]
+  static classes = [ "grouped" ]
+
+  notificationTargetConnected(notification) {
+    this.#groupNotificationIfNeeded(notification)
+  }
+
+  #groupNotificationIfNeeded(notification) {
+    const groupedNotifications = this.#groupedNotificationsFor(notification)
+
+    if (groupedNotifications.length > 1) {
+      this.#renderGroup(groupedNotifications)
+    }
+  }
+
+  #groupedNotificationsFor(notification) {
+    const cardId = notification.dataset.cardId
+    return this.notificationTargets
+      .filter(notification => notification.dataset.cardId === cardId)
+      .sort((notification_1, notification_2) => parseInt(notification_1.dataset.timestamp) - parseInt(notification_2.dataset.timestamp))
+  }
+
+  #renderGroup(groupedNotifications) {
+    this.#showAsGrouped(groupedNotifications[0], groupedNotifications.length)
+    groupedNotifications.slice(1).forEach(notification => this.#hideInGroup(notification))
+  }
+
+  #showAsGrouped(notification, size) {
+    notification.classList.add(this.groupedClass)
+    this.#showGroupedNotification(notification)
+    this.#setGroupCount(notification, size)
+  }
+
+  #hideInGroup(notification) {
+    this.#hideGroupedNotification(notification)
+    this.#setGroupCount(notification, "")
+  }
+
+  // We use a hidden container instead of hiding the notifications directly so that the CSS that sort the
+  // tray element indexes doesn't get messed up.
+  #showGroupedNotification(notification) {
+    if (notification.parentElement === this.hiddenNotificationsTarget) {
+      this.hiddenNotificationsTarget.parentElement.insertBefore(notification, this.hiddenNotificationsTarget)
+    }
+  }
+
+  #hideGroupedNotification(notification) {
+    this.hiddenNotificationsTarget.appendChild(notification)
+  }
+
+  #setGroupCount(notification, count) {
+    notification.querySelector("[data-group-count]").textContent = count
+  }
+}
diff --git a/app/views/notifications/_notification.html.erb b/app/views/notifications/_notification.html.erb
index b945960b8..49abafcb6 100644
--- a/app/views/notifications/_notification.html.erb
+++ b/app/views/notifications/_notification.html.erb
@@ -3,6 +3,7 @@
 
     <header class="card__header">
       <%= render "notifications/notification/#{notification.source_type.underscore}/header", notification: notification %>
+      <span data-group-count></span>
     </header>
 
     <div class="card__body">
diff --git a/app/views/notifications/_tray.html.erb b/app/views/notifications/_tray.html.erb
index a009835a4..d2fa40a5d 100644
--- a/app/views/notifications/_tray.html.erb
+++ b/app/views/notifications/_tray.html.erb
@@ -7,7 +7,7 @@
       data-navigable-list-actionable-items-value="true"
       data-navigable-list-reverse-navigation-value="true"
       data-action="keydown->navigable-list#navigate dialog:show@document->navigable-list#reset turbo-visit->navigable-list#reset keydown.esc->dialog#close:stop click@document->dialog#closeOnClickOutside">
-    <%= turbo_frame_tag "notifications", src: tray_notifications_path, refresh: "morph" %>
+    <%= turbo_frame_tag "notifications", src: tray_notifications_path, refresh: "morph", data: { controller: "notifications-tray", notifications_tray_grouped_class: "notification--grouped" } %>
 
     <div class="tray__item tray__item--hat txt-x-small gap-half">
       <div data-navigable-list-target="item" class="full-width">
diff --git a/app/views/notifications/trays/show.html.erb b/app/views/notifications/trays/show.html.erb
index f61c52d51..a4700253b 100644
--- a/app/views/notifications/trays/show.html.erb
+++ b/app/views/notifications/trays/show.html.erb
@@ -1,3 +1,4 @@
-<%= turbo_frame_tag "notifications" do %>
+<%= turbo_frame_tag "notifications", data: { controller: "notifications-tray", notifications_tray_grouped_class: "notification--grouped" } do %>
   <%= render partial: "notifications/notification", collection: @notifications, cached: true %>
+  <div hidden data-notifications-tray-target="hiddenNotifications"></div>
 <% end %>