diff --git a/core/modules/outside_in/js/outside_in.js b/core/modules/outside_in/js/outside_in.js
index 0b8bc88..cb5c3cc 100644
--- a/core/modules/outside_in/js/outside_in.js
+++ b/core/modules/outside_in/js/outside_in.js
@@ -77,7 +77,7 @@
    * Helper to toggle Edit mode.
    */
   function toggleEditMode() {
-    setEditModeState(!isInEditMode());
+    setEditModeState(!isInEditMode(), true);
   }
 
   /**
@@ -118,20 +118,41 @@
   }
 
   /**
+   * Display message describing edit mode.
+   *
+   * @todo Refactor to use Javascript Message API https://www.drupal.org/node/77245
+   */
+  function displayEditMessage() {
+    var msgDiv = document.createElement('div');
+    msgDiv.setAttribute('class', 'settings-tray-messages messages messages--status');
+    msgDiv.setAttribute('role', 'alert');
+    msgDiv.innerHTML = 'You are now in edit mode.';
+    $(msgDiv).insertBefore('div.dialog-offcanvas__main-canvas').hide().fadeIn('slow');
+    $(msgDiv).on('click.outsidein', function (e) {
+      $(e.target).remove();
+    });
+  }
+
+  /**
    *  Helper to switch edit mode state.
    *
    * @param {boolean} editMode
    *  True enable edit mode, false disable edit mode.
+   * @param {boolean} displayMessage
+   *  True display edit mode message when starting, false do not show message.
    */
-  function setEditModeState(editMode) {
+  function setEditModeState(editMode, displayMessage) {
     editMode = !!editMode;
+    displayMessage = (displayMessage !== false);
     var $editButton = $(toggleEditSelector);
     var $editables;
     // Turn on edit mode.
     if (editMode) {
       $editButton.text(Drupal.t('Editing'));
       closeToolbarTrays();
-
+      if (displayMessage) {
+        displayEditMessage();
+      }
       $editables = $('[data-drupal-outsidein="editable"]').once('outsidein');
       if ($editables.length) {
         // Use event capture to prevent clicks on links.
@@ -167,6 +188,7 @@
     // Disable edit mode.
     else {
       $editables = $('[data-drupal-outsidein="editable"]').removeOnce('outsidein');
+      $('.settings-tray-messages').remove();
       if ($editables.length) {
         document.querySelector('[data-offcanvas-main-canvas]').removeEventListener('click', preventClick, true);
         $editables.off('.outsidein');
@@ -192,8 +214,9 @@
   Drupal.behaviors.outsideInEdit = {
     attach: function () {
       var editMode = localStorage.getItem('Drupal.contextualToolbar.isViewing') === 'false';
-      if (editMode) {
-        setEditModeState(true);
+      // Enter Edit mode if set in local storage and not currently in edit mode.
+      if (editMode && !isInEditMode()) {
+        setEditModeState(true, false);
       }
     }
   };
diff --git a/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php b/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php
index 04c6e70..d57cc19 100644
--- a/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php
+++ b/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInBlockFormTest.php
@@ -166,15 +166,19 @@ public function providerTestBlocks() {
    * Enables Editing mode by pressing "Edit" button in the toolbar.
    */
   protected function toggleEditingMode() {
-    $this->assertSession()->waitForElementVisible('css', 'div[data-contextual-id="block:block=powered:langcode=en|outside_in::langcode=en"] .contextual-links a', 10000);
-    // Waiting for QuickEdit icon animation.
-    $this->assertSession()->assertWaitOnAjaxRequest();
+    $page = $this->getSession()->getPage();
+    $in_edit_mode = $page->has('css', 'div.dialog-offcanvas__main-canvas.js-outside-in-edit-mode');
 
-    $edit_button = $this->getSession()->getPage()->find('css', '#toolbar-bar div.contextual-toolbar-tab button');
+    $edit_button = $page->find('css', '#toolbar-bar div.contextual-toolbar-tab button');
 
     $edit_button->press();
-    // Waiting for Toolbar animation.
     $this->assertSession()->assertWaitOnAjaxRequest();
+    if (!$in_edit_mode) {
+      $this->assertSession()->elementTextContains('css', '.settings-tray-messages', 'You are now in edit mode.');
+    }
+    else {
+      $this->assertSession()->elementNotExists('css', '.settings-tray-messages');
+    }
   }
 
   /**