diff --git a/packages/e2e-tests/specs/editor/plugins/__snapshots__/plugins-api.test.js.snap b/packages/e2e-tests/specs/editor/plugins/__snapshots__/plugins-api.test.js.snap
index f823deeb3965f8..8d2ca2c2bd9a78 100644
--- a/packages/e2e-tests/specs/editor/plugins/__snapshots__/plugins-api.test.js.snap
+++ b/packages/e2e-tests/specs/editor/plugins/__snapshots__/plugins-api.test.js.snap
@@ -2,6 +2,6 @@
 
 exports[`Using Plugins API Document Setting Custom Panel Should render a custom panel inside Document Setting sidebar 1`] = `"My Custom Panel"`;
 
-exports[`Using Plugins API Sidebar Medium screen Should open plugins sidebar using More Menu item and render content 1`] = `"<div class=\\"components-panel__header edit-post-sidebar-header__small\\"><span class=\\"edit-post-sidebar-header__title\\">(no title)</span><button type=\\"button\\" class=\\"components-button has-icon\\" aria-label=\\"Close plugin\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"0 0 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M13 11.8l6.1-6.3-1-1-6.1 6.2-6.1-6.2-1 1 6.1 6.3-6.5 6.7 1 1 6.5-6.6 6.5 6.6 1-1z\\"></path></svg></button></div><div class=\\"components-panel__header edit-post-sidebar-header\\"><strong>Sidebar title plugin</strong><button type=\\"button\\" aria-pressed=\\"true\\" aria-expanded=\\"true\\" class=\\"components-button is-pressed has-icon\\" aria-label=\\"Unpin from toolbar\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"-2 -2 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M10 1l3 6 6 .75-4.12 4.62L16 19l-6-3-6 3 1.13-6.63L1 7.75 7 7z\\"></path></svg></button><button type=\\"button\\" class=\\"components-button has-icon\\" aria-label=\\"Close plugin\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"0 0 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M13 11.8l6.1-6.3-1-1-6.1 6.2-6.1-6.2-1 1 6.1 6.3-6.5 6.7 1 1 6.5-6.6 6.5 6.6 1-1z\\"></path></svg></button></div><div class=\\"components-panel\\"><div class=\\"components-panel__body is-opened\\"><div class=\\"components-panel__row\\"><label for=\\"title-plain-text\\">Title:</label><textarea class=\\"block-editor-plain-text\\" id=\\"title-plain-text\\" placeholder=\\"(no title)\\" rows=\\"1\\" style=\\"overflow: hidden; overflow-wrap: break-word; resize: none; height: 18px;\\"></textarea></div><div class=\\"components-panel__row\\"><button type=\\"button\\" class=\\"components-button is-primary\\">Reset</button></div></div></div>"`;
+exports[`Using Plugins API Sidebar Medium screen Should open plugins sidebar using More Menu item and render content 1`] = `"<div class=\\"components-panel__header edit-post-sidebar-header__small\\"><span class=\\"edit-post-sidebar-header__title\\">(no title)</span><button type=\\"button\\" class=\\"components-button has-icon\\" aria-label=\\"Close plugin\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"0 0 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M13 11.8l6.1-6.3-1-1-6.1 6.2-6.1-6.2-1 1 6.1 6.3-6.5 6.7 1 1 6.5-6.6 6.5 6.6 1-1z\\"></path></svg></button></div><div class=\\"components-panel__header edit-post-sidebar-header\\" tabindex=\\"-1\\"><strong>Sidebar title plugin</strong><button type=\\"button\\" aria-pressed=\\"true\\" aria-expanded=\\"true\\" class=\\"components-button is-pressed has-icon\\" aria-label=\\"Unpin from toolbar\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"-2 -2 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M10 1l3 6 6 .75-4.12 4.62L16 19l-6-3-6 3 1.13-6.63L1 7.75 7 7z\\"></path></svg></button><button type=\\"button\\" class=\\"components-button has-icon\\" aria-label=\\"Close plugin\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"0 0 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M13 11.8l6.1-6.3-1-1-6.1 6.2-6.1-6.2-1 1 6.1 6.3-6.5 6.7 1 1 6.5-6.6 6.5 6.6 1-1z\\"></path></svg></button></div><div class=\\"components-panel\\"><div class=\\"components-panel__body is-opened\\"><div class=\\"components-panel__row\\"><label for=\\"title-plain-text\\">Title:</label><textarea class=\\"block-editor-plain-text\\" id=\\"title-plain-text\\" placeholder=\\"(no title)\\" rows=\\"1\\" style=\\"overflow: hidden; overflow-wrap: break-word; resize: none; height: 18px;\\"></textarea></div><div class=\\"components-panel__row\\"><button type=\\"button\\" class=\\"components-button is-primary\\">Reset</button></div></div></div>"`;
 
-exports[`Using Plugins API Sidebar Should open plugins sidebar using More Menu item and render content 1`] = `"<div class=\\"components-panel__header edit-post-sidebar-header__small\\"><span class=\\"edit-post-sidebar-header__title\\">(no title)</span><button type=\\"button\\" class=\\"components-button has-icon\\" aria-label=\\"Close plugin\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"0 0 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M13 11.8l6.1-6.3-1-1-6.1 6.2-6.1-6.2-1 1 6.1 6.3-6.5 6.7 1 1 6.5-6.6 6.5 6.6 1-1z\\"></path></svg></button></div><div class=\\"components-panel__header edit-post-sidebar-header\\"><strong>Sidebar title plugin</strong><button type=\\"button\\" aria-pressed=\\"true\\" aria-expanded=\\"true\\" class=\\"components-button is-pressed has-icon\\" aria-label=\\"Unpin from toolbar\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"-2 -2 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M10 1l3 6 6 .75-4.12 4.62L16 19l-6-3-6 3 1.13-6.63L1 7.75 7 7z\\"></path></svg></button><button type=\\"button\\" class=\\"components-button has-icon\\" aria-label=\\"Close plugin\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"0 0 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M13 11.8l6.1-6.3-1-1-6.1 6.2-6.1-6.2-1 1 6.1 6.3-6.5 6.7 1 1 6.5-6.6 6.5 6.6 1-1z\\"></path></svg></button></div><div class=\\"components-panel\\"><div class=\\"components-panel__body is-opened\\"><div class=\\"components-panel__row\\"><label for=\\"title-plain-text\\">Title:</label><textarea class=\\"block-editor-plain-text\\" id=\\"title-plain-text\\" placeholder=\\"(no title)\\" rows=\\"1\\" style=\\"overflow: hidden; overflow-wrap: break-word; resize: none; height: 18px;\\"></textarea></div><div class=\\"components-panel__row\\"><button type=\\"button\\" class=\\"components-button is-primary\\">Reset</button></div></div></div>"`;
+exports[`Using Plugins API Sidebar Should open plugins sidebar using More Menu item and render content 1`] = `"<div class=\\"components-panel__header edit-post-sidebar-header__small\\"><span class=\\"edit-post-sidebar-header__title\\">(no title)</span><button type=\\"button\\" class=\\"components-button has-icon\\" aria-label=\\"Close plugin\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"0 0 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M13 11.8l6.1-6.3-1-1-6.1 6.2-6.1-6.2-1 1 6.1 6.3-6.5 6.7 1 1 6.5-6.6 6.5 6.6 1-1z\\"></path></svg></button></div><div class=\\"components-panel__header edit-post-sidebar-header\\" tabindex=\\"-1\\"><strong>Sidebar title plugin</strong><button type=\\"button\\" aria-pressed=\\"true\\" aria-expanded=\\"true\\" class=\\"components-button is-pressed has-icon\\" aria-label=\\"Unpin from toolbar\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"-2 -2 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M10 1l3 6 6 .75-4.12 4.62L16 19l-6-3-6 3 1.13-6.63L1 7.75 7 7z\\"></path></svg></button><button type=\\"button\\" class=\\"components-button has-icon\\" aria-label=\\"Close plugin\\"><svg width=\\"24\\" height=\\"24\\" xmlns=\\"http://www.w3.org/2000/svg\\" viewBox=\\"0 0 24 24\\" role=\\"img\\" aria-hidden=\\"true\\" focusable=\\"false\\"><path d=\\"M13 11.8l6.1-6.3-1-1-6.1 6.2-6.1-6.2-1 1 6.1 6.3-6.5 6.7 1 1 6.5-6.6 6.5 6.6 1-1z\\"></path></svg></button></div><div class=\\"components-panel\\"><div class=\\"components-panel__body is-opened\\"><div class=\\"components-panel__row\\"><label for=\\"title-plain-text\\">Title:</label><textarea class=\\"block-editor-plain-text\\" id=\\"title-plain-text\\" placeholder=\\"(no title)\\" rows=\\"1\\" style=\\"overflow: hidden; overflow-wrap: break-word; resize: none; height: 18px;\\"></textarea></div><div class=\\"components-panel__row\\"><button type=\\"button\\" class=\\"components-button is-primary\\">Reset</button></div></div></div>"`;
diff --git a/packages/edit-post/src/components/sidebar/sidebar-header/index.js b/packages/edit-post/src/components/sidebar/sidebar-header/index.js
index 84bd69b07e7048..748992e82b0426 100644
--- a/packages/edit-post/src/components/sidebar/sidebar-header/index.js
+++ b/packages/edit-post/src/components/sidebar/sidebar-header/index.js
@@ -23,6 +23,14 @@ const SidebarHeader = ( { children, className, closeLabel } ) => {
 	);
 	const { closeGeneralSidebar } = useDispatch( 'core/edit-post' );
 
+	// The `tabIndex` serves the purpose of normalizing browser behavior of
+	// button clicks and focus. Notably, without making the header focusable, a
+	// Button click would not trigger a focus event in macOS Firefox. Thus, when
+	// the sidebar is unmounted, the corresponding "focus return" behavior to
+	// shift focus back to the heading toolbar would not be run.
+	//
+	// See: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/button#Clicking_and_focus
+
 	return (
 		<>
 			<div className="components-panel__header edit-post-sidebar-header__small">
@@ -40,6 +48,7 @@ const SidebarHeader = ( { children, className, closeLabel } ) => {
 					'components-panel__header edit-post-sidebar-header',
 					className
 				) }
+				tabIndex={ -1 }
 			>
 				{ children }
 				<Button