diff --git a/_release-content/migration-guides/observe_bundle_helper_deprecation.md b/_release-content/migration-guides/observe_bundle_helper_deprecation.md
new file mode 100644
index 0000000000000..2de24e47959ac
--- /dev/null
+++ b/_release-content/migration-guides/observe_bundle_helper_deprecation.md
@@ -0,0 +1,34 @@
+---
+title: "`bevy_ui_widgets::observe` has been deprecated in favor of `bsn!`"
+pull_requests: [23730]
+---
+
+The `observe` function and `AddObserver` struct in `bevy_ui_widgets` have been deprecated.
+These were a workaround for attaching observers as bundle effects.
+Now that `bsn!` supports the `on` helper natively, use that instead.
+
+Before:
+
+```rust
+use bevy_ui_widgets::observe;
+
+commands.spawn((
+    Button,
+    observe(|_event: On<Pointer<Press>>| {
+        println!("Clicked!");
+    }),
+));
+```
+
+After:
+
+```rust
+commands.spawn(bsn! {
+    Button
+    on(|_event: On<Pointer<Press>>| {
+        println!("Clicked!");
+    })
+});
+```
+
+If you were using `AddObserver` directly for some reason, replace it with `on` inside a `bsn!` block in the same way.
diff --git a/crates/bevy_feathers/src/controls/virtual_keyboard.rs b/crates/bevy_feathers/src/controls/virtual_keyboard.rs
index 3d87a3c99fd00..9ddc93b03cca1 100644
--- a/crates/bevy_feathers/src/controls/virtual_keyboard.rs
+++ b/crates/bevy_feathers/src/controls/virtual_keyboard.rs
@@ -81,7 +81,7 @@ where
 ///
 ///  These events can be disabled by adding an [`bevy_ui::InteractionDisabled`] component to the entity
 #[deprecated(since = "0.19.0", note = "Use the virtual_keyboard() BSN function")]
-#[expect(deprecated, reason = "uses the deprecated button_bundle")]
+#[expect(deprecated, reason = "uses the deprecated button_bundle and observe")]
 pub fn virtual_keyboard_bundle<T>(
     keys: impl Iterator<Item = Vec<T>> + Send + Sync + 'static,
 ) -> impl Bundle
diff --git a/crates/bevy_ui_widgets/src/observe.rs b/crates/bevy_ui_widgets/src/observe.rs
index 944d0c198dd21..cbeef48df39e8 100644
--- a/crates/bevy_ui_widgets/src/observe.rs
+++ b/crates/bevy_ui_widgets/src/observe.rs
@@ -1,6 +1,8 @@
-// TODO: This probably doesn't belong in bevy_ui_widgets, but I am not sure where it should go.
-// It is certainly a useful thing to have.
 #![expect(unsafe_code, reason = "Unsafe code is used to improve performance.")]
+#![expect(
+    deprecated,
+    reason = "We need to use the pre-existing tools until this is removed."
+)]
 
 use core::{marker::PhantomData, mem};
 
@@ -11,6 +13,10 @@ use bevy_ecs::{
 };
 
 /// Helper struct that adds an observer when inserted as a [`Bundle`].
+#[deprecated(
+    since = "0.19.0",
+    note = "Use the `on` helper with bsn! instead to spawn observers as part of ECS hierarchies."
+)]
 pub struct AddObserver<E: EntityEvent, B: Bundle, M, I: IntoObserverSystem<E, B, M>> {
     observer: I,
     marker: PhantomData<(E, B, M)>,
@@ -74,6 +80,10 @@ impl<E: EntityEvent, B: Bundle, M, I: IntoObserverSystem<E, B, M>> DynamicBundle
 }
 
 /// Adds an observer as a bundle effect.
+#[deprecated(
+    since = "0.19.0",
+    note = "Use the `on` helper with bsn! instead to spawn observers as part of ECS hierarchies."
+)]
 pub fn observe<E: EntityEvent, B: Bundle, M, I: IntoObserverSystem<E, B, M>>(
     observer: I,
 ) -> AddObserver<E, B, M, I> {