diff --git a/browser/app/profile/firefox.js b/browser/app/profile/firefox.js
index dfaaa051dfca..a6aa3f9cba4c 100644
--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -675,6 +675,9 @@ pref("accessibility.typeaheadfind.timeout", 5000);
 pref("accessibility.typeaheadfind.linksonly", false);
 pref("accessibility.typeaheadfind.flashBar", 1);
 
+// Tracks when accessibility is loaded into the previous session.
+pref("accessibility.loadedInLastSession", false);
+
 pref("plugins.click_to_play", true);
 pref("plugins.testmode", false);
 
@@ -988,6 +991,9 @@ pref("toolkit.crashreporter.infoURL",
 // base URL for web-based support pages
 pref("app.support.baseURL", "https://support.mozilla.org/1/firefox/%VERSION%/%OS%/%LOCALE%/");
 
+// a11y conflicts with e10s support page
+pref("app.support.e10sAccessibilityUrl", "https://support.mozilla.org/1/firefox/%VERSION%/%OS%/%LOCALE%/accessibility-ppt");
+
 // base url for web-based feedback pages
 #ifdef MOZ_DEV_EDITION
 pref("app.feedback.baseURL", "https://input.mozilla.org/%LOCALE%/feedback/firefoxdev/%VERSION%/");
diff --git a/browser/components/nsBrowserGlue.js b/browser/components/nsBrowserGlue.js
index 15e4b52e7425..a9ec7dda5c22 100644
--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -532,6 +532,13 @@ BrowserGlue.prototype = {
 
     this._flashHangCount = 0;
     this._firstWindowReady = new Promise(resolve => this._firstWindowLoaded = resolve);
+
+    if (AppConstants.platform == "macosx" ||
+        (AppConstants.platform == "win" && AppConstants.RELEASE_OR_BETA)) {
+      // Handles prompting to inform about incompatibilites when accessibility
+      // and e10s are active together.
+      E10SAccessibilityCheck.init();
+    }
   },
 
   // cleanup (called on application shutdown)
@@ -1058,7 +1065,10 @@ BrowserGlue.prototype = {
     }
 
     this._sanitizer.onStartup();
+    E10SAccessibilityCheck.onWindowsRestored();
+
     this._scheduleStartupIdleTasks();
+
     this._lateTasksIdleObserver = (idleService, topic, data) => {
       if (topic == "idle") {
         idleService.removeIdleObserver(this._lateTasksIdleObserver,
@@ -2825,9 +2835,132 @@ var DefaultBrowserCheck = {
   },
 };
 
+var E10SAccessibilityCheck = {
+  // tracks when an a11y init observer fires prior to the
+  // first window being opening.
+  _wantsPrompt: false,
+
+  init() {
+    Services.obs.addObserver(this, "a11y-init-or-shutdown", true);
+    Services.obs.addObserver(this, "quit-application-granted", true);
+  },
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
+
+  get forcedOn() {
+    try {
+      return Services.prefs.getBoolPref("browser.tabs.remote.force-enable");
+    } catch (e) {}
+    return false;
+  },
+
+  observe(subject, topic, data) {
+    switch (topic) {
+      case "quit-application-granted":
+        // Tag the profile with a11y load state. We use this in nsAppRunner
+        // checks on the next start.
+        Services.prefs.setBoolPref("accessibility.loadedInLastSession",
+                                   Services.appinfo.accessibilityEnabled);
+        break;
+      case "a11y-init-or-shutdown":
+        if (data == "1") {
+          // Update this so users can check this while still running
+          Services.prefs.setBoolPref("accessibility.loadedInLastSession", true);
+          this._showE10sAccessibilityWarning();
+        }
+        break;
+    }
+  },
+
+  onWindowsRestored() {
+    if (this._wantsPrompt) {
+      this._wantsPrompt = false;
+      this._showE10sAccessibilityWarning();
+    }
+  },
+
+  _warnedAboutAccessibility: false,
+
+  _showE10sAccessibilityWarning() {
+    // We don't prompt about a11y incompat if e10s is off.
+    if (!Services.appinfo.browserTabsRemoteAutostart) {
+      return;
+    }
+
+    // If the user set the forced pref and it's true, ignore a11y init.
+    // If the pref doesn't exist or if it's false, prompt.
+    if (this.forcedOn) {
+      return;
+    }
+
+    // Only prompt once per session
+    if (this._warnedAboutAccessibility) {
+      return;
+    }
+    this._warnedAboutAccessibility = true;
+
+    let win = RecentWindow.getMostRecentBrowserWindow();
+    if (!win || !win.gBrowser || !win.gBrowser.selectedBrowser) {
+      Services.console.logStringMessage(
+          "Accessibility support is partially disabled due to compatibility issues with new features.");
+      this._wantsPrompt = true;
+      this._warnedAboutAccessibility = false;
+      return;
+    }
+    let browser = win.gBrowser.selectedBrowser;
+
+    // We disable a11y for content and prompt on the chrome side letting
+    // a11y users know they need to disable e10s and restart.
+    let promptMessage = win.gNavigatorBundle.getFormattedString(
+                          "e10s.accessibilityNotice.mainMessage2",
+                          [gBrandBundle.GetStringFromName("brandShortName")]
+                        );
+    let notification;
+    let restartCallback  = function() {
+      let cancelQuit = Cc["@mozilla.org/supports-PRBool;1"].createInstance(Ci.nsISupportsPRBool);
+      Services.obs.notifyObservers(cancelQuit, "quit-application-requested", "restart");
+      if (cancelQuit.data) {
+        return; // somebody canceled our quit request
+      }
+      // Restart the browser
+      Services.startup.quit(Services.startup.eAttemptQuit | Services.startup.eRestart);
+    };
+    // main option: an Ok button, keeps running with content accessibility disabled
+    let mainAction = {
+      label: win.gNavigatorBundle.getString("e10s.accessibilityNotice.acceptButton.label"),
+      accessKey: win.gNavigatorBundle.getString("e10s.accessibilityNotice.acceptButton.accesskey"),
+      callback() {
+        // If the user invoked the button option remove the notification,
+        // otherwise keep the alert icon around in the address bar.
+        notification.remove();
+      },
+      dismiss: true
+    };
+    // secondary option: a restart now button. When we restart e10s will be disabled due to
+    // accessibility having been loaded in the previous session.
+    let secondaryActions = [{
+      label: win.gNavigatorBundle.getString("e10s.accessibilityNotice.enableAndRestart.label"),
+      accessKey: win.gNavigatorBundle.getString("e10s.accessibilityNotice.enableAndRestart.accesskey"),
+      callback: restartCallback,
+    }];
+    let options = {
+      popupIconURL: "chrome://browser/skin/e10s-64@2x.png",
+      learnMoreURL: Services.urlFormatter.formatURLPref("app.support.e10sAccessibilityUrl"),
+      persistent: true,
+      persistWhileVisible: true,
+    };
+
+    notification =
+      win.PopupNotifications.show(browser, "a11y_enabled_with_e10s",
+                                  promptMessage, null, mainAction,
+                                  secondaryActions, options);
+  },
+};
+
 var components = [BrowserGlue, ContentPermissionPrompt];
 this.NSGetFactory = XPCOMUtils.generateNSGetFactory(components);
 
+
 // Listen for UITour messages.
 // Do it here instead of the UITour module itself so that the UITour module is lazy loaded
 // when the first message is received.
diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index eadcc8160839..d81f585806f0 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -267,6 +267,11 @@
 
 static NS_DEFINE_CID(kCClipboardCID, NS_CLIPBOARD_CID);
 
+#if defined(XP_WIN)
+// e10s forced enable pref, defined in nsAppRunner.cpp
+extern const char* kForceEnableE10sPref;
+#endif
+
 using base::ChildPrivileges;
 using base::KillProcess;
 
@@ -1305,8 +1310,13 @@ ContentParent::Init()
   // process.
   if (nsIPresShell::IsAccessibilityActive()) {
 #if defined(XP_WIN)
-    Unused << SendActivateA11y(::GetCurrentThreadId(),
-                                a11y::AccessibleWrap::GetContentProcessIdFor(ChildID()));
+#if defined(RELEASE_OR_BETA)
+    // On Windows we currently only enable a11y in the content process
+    // for testing purposes.
+    if (Preferences::GetBool(kForceEnableE10sPref, false))
+#endif
+      Unused << SendActivateA11y(::GetCurrentThreadId(),
+                                 a11y::AccessibleWrap::GetContentProcessIdFor(ChildID()));
 #else
     Unused << SendActivateA11y(0, 0);
 #endif
@@ -2840,8 +2850,13 @@ ContentParent::Observe(nsISupports* aSubject,
       // Make sure accessibility is running in content process when
       // accessibility gets initiated in chrome process.
 #if defined(XP_WIN)
-      Unused << SendActivateA11y(::GetCurrentThreadId(),
-                                  a11y::AccessibleWrap::GetContentProcessIdFor(ChildID()));
+#if defined(RELEASE_OR_BETA)
+      // On Windows we currently only enable a11y in the content process
+      // for testing purposes.
+      if (Preferences::GetBool(kForceEnableE10sPref, false))
+#endif
+        Unused << SendActivateA11y(::GetCurrentThreadId(),
+                                   a11y::AccessibleWrap::GetContentProcessIdFor(ChildID()));
 #else
       Unused << SendActivateA11y(0, 0);
 #endif
diff --git a/toolkit/xre/nsAppRunner.cpp b/toolkit/xre/nsAppRunner.cpp
index 43734af69ea6..6c16dd1f791a 100644
--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -5049,7 +5049,7 @@ enum {
   kE10sEnabledByDefault = 1,
   kE10sDisabledByUser = 2,
   // kE10sDisabledInSafeMode = 3, was removed in bug 1172491.
-  // kE10sDisabledForAccessibility = 4,
+  kE10sDisabledForAccessibility = 4,
   // kE10sDisabledForMacGfx = 5, was removed in bug 1068674.
   // kE10sDisabledForBidi = 6, removed in bug 1309599
   kE10sDisabledForAddons = 7,
@@ -5058,6 +5058,18 @@ enum {
   // kE10sDisabledForOperatingSystem = 10, removed due to xp-eol
 };
 
+const char* kAccessibilityLastRunDatePref = "accessibility.lastLoadDate";
+const char* kAccessibilityLoadedLastSessionPref = "accessibility.loadedInLastSession";
+
+#if defined(XP_WIN)
+static inline uint32_t
+PRTimeToSeconds(PRTime t_usec)
+{
+  PRTime usec_per_sec = PR_USEC_PER_SEC;
+  return uint32_t(t_usec /= usec_per_sec);
+}
+#endif
+
 const char* kForceEnableE10sPref = "browser.tabs.remote.force-enable";
 const char* kForceDisableE10sPref = "browser.tabs.remote.force-disable";
 
@@ -5085,6 +5097,40 @@ MultiprocessBlockPolicy()
     return kE10sDisabledForAddons;
   }
 
+#if defined(XP_WIN) && defined(RELEASE_OR_BETA)
+  bool disabledForA11y = false;
+  /**
+    * Avoids enabling e10s if accessibility has recently loaded. Performs the
+    * following checks:
+    * 1) Checks a pref indicating if a11y loaded in the last session. This pref
+    * is set in nsBrowserGlue.js. If a11y was loaded in the last session we
+    * do not enable e10s in this session.
+    * 2) Accessibility stores a last run date (PR_IntervalNow) when it is
+    * initialized (see nsBaseWidget.cpp). We check if this pref exists and
+    * compare it to now. If a11y hasn't run in an extended period of time or
+    * if the date pref does not exist we load e10s.
+    */
+  disabledForA11y = Preferences::GetBool(kAccessibilityLoadedLastSessionPref, false);
+  if (!disabledForA11y  &&
+      Preferences::HasUserValue(kAccessibilityLastRunDatePref)) {
+    const uint32_t oneWeekInSeconds = 60 * 60 * 24 * 7;
+    uint32_t a11yRunDate = Preferences::GetInt(kAccessibilityLastRunDatePref, 0);
+    MOZ_ASSERT(0 != a11yRunDate);
+    // If a11y hasn't run for a period of time, clear the pref and load e10s
+    uint32_t now = PRTimeToSeconds(PR_Now());
+    uint32_t difference = now - a11yRunDate;
+    if (difference > oneWeekInSeconds || !a11yRunDate) {
+      Preferences::ClearUser(kAccessibilityLastRunDatePref);
+    } else {
+      disabledForA11y = true;
+    }
+  }
+
+  if (disabledForA11y) {
+    return kE10sDisabledForAccessibility;
+  }
+#endif
+
   /*
    * None of the blocking policies matched, so e10s is allowed to run. Return
    * 0, indicating success.
diff --git a/widget/nsBaseWidget.cpp b/widget/nsBaseWidget.cpp
index 0e8631aeea1d..7543451d7d61 100644
--- a/widget/nsBaseWidget.cpp
+++ b/widget/nsBaseWidget.cpp
@@ -171,6 +171,9 @@ nsBaseWidget::nsBaseWidget()
 , mUseAttachedEvents(false)
 , mIMEHasFocus(false)
 , mIsFullyOccluded(false)
+#if defined(XP_WIN) || defined(XP_MACOSX) || defined(MOZ_WIDGET_GTK)
+, mAccessibilityInUseFlag(false)
+#endif
 {
 #ifdef NOISY_WIDGET_LEAKS
   gNumWidgets++;
@@ -1883,6 +1886,18 @@ nsBaseWidget::ZoomToRect(const uint32_t& aPresShellId,
 
 #ifdef ACCESSIBILITY
 
+#if defined(XP_WIN) || defined(XP_MACOSX) || defined(MOZ_WIDGET_GTK)
+// defined in nsAppRunner.cpp
+extern const char* kAccessibilityLastRunDatePref;
+
+static inline uint32_t
+PRTimeToSeconds(PRTime t_usec)
+{
+  PRTime usec_per_sec = PR_USEC_PER_SEC;
+  return uint32_t(t_usec /= usec_per_sec);
+}
+#endif
+
 a11y::Accessible*
 nsBaseWidget::GetRootAccessible()
 {
@@ -1900,6 +1915,13 @@ nsBaseWidget::GetRootAccessible()
   // make sure it's not created at unsafe times.
   nsAccessibilityService* accService = GetOrCreateAccService();
   if (accService) {
+#if defined(XP_WIN) || defined(XP_MACOSX) || defined(MOZ_WIDGET_GTK)
+    if (!mAccessibilityInUseFlag) {
+      mAccessibilityInUseFlag = true;
+      uint32_t now = PRTimeToSeconds(PR_Now());
+      Preferences::SetInt(kAccessibilityLastRunDatePref, now);
+    }
+#endif
     return accService->GetRootDocumentAccessible(presShell, nsContentUtils::IsSafeToRunScript());
   }
 
diff --git a/widget/nsBaseWidget.h b/widget/nsBaseWidget.h
index b92b78ecebb3..9146215ef172 100644
--- a/widget/nsBaseWidget.h
+++ b/widget/nsBaseWidget.h
@@ -695,6 +695,9 @@ protected:
   bool              mUseAttachedEvents;
   bool              mIMEHasFocus;
   bool              mIsFullyOccluded;
+#if defined(XP_WIN) || defined(XP_MACOSX) || defined(MOZ_WIDGET_GTK)
+  bool              mAccessibilityInUseFlag;
+#endif
   static nsIRollupListener* gRollupListener;
 
   struct InitialZoomConstraints {