diff --git a/testing/marionette/client/marionette/__init__.py b/testing/marionette/client/marionette/__init__.py
index 0f42de010171..67a263367d59 100644
--- a/testing/marionette/client/marionette/__init__.py
+++ b/testing/marionette/client/marionette/__init__.py
@@ -8,6 +8,7 @@ from marionette import Marionette, HTMLElement, Actions, MultiActions
 from marionette_test import MarionetteTestCase, MarionetteJSTestCase, CommonTestCase, expectedFailure, skip, SkipTest
 from errors import (
     ElementNotVisibleException,
+    ElementNotAccessibleException,
     ErrorCodes,
     FrameSendFailureError,
     FrameSendNotInitializedError,
diff --git a/testing/marionette/client/marionette/errors.py b/testing/marionette/client/marionette/errors.py
index aee6aa24c52f..81ca613bfc4b 100644
--- a/testing/marionette/client/marionette/errors.py
+++ b/testing/marionette/client/marionette/errors.py
@@ -13,6 +13,7 @@ class ErrorCodes(object):
     ELEMENT_NOT_VISIBLE = 11
     INVALID_ELEMENT_STATE = 12
     UNKNOWN_ERROR = 13
+    ELEMENT_NOT_ACCESSIBLE = 56
     ELEMENT_IS_NOT_SELECTABLE = 15
     JAVASCRIPT_ERROR = 17
     XPATH_LOOKUP_ERROR = 19
@@ -113,6 +114,9 @@ class ElementNotVisibleException(MarionetteException):
         super(ElementNotVisibleException, self).__init__(
             message, status=status, cause=cause, stacktrace=stacktrace)
 
+class ElementNotAccessibleException(MarionetteException):
+    pass
+
 class NoSuchFrameException(MarionetteException):
     pass
 
diff --git a/testing/marionette/client/marionette/marionette.py b/testing/marionette/client/marionette/marionette.py
index 35a7fee5a0b6..75a8ee91ccbd 100644
--- a/testing/marionette/client/marionette/marionette.py
+++ b/testing/marionette/client/marionette/marionette.py
@@ -677,6 +677,8 @@ class Marionette(object):
             raise errors.StaleElementException(message=message, status=status, stacktrace=stacktrace)
         elif status == errors.ErrorCodes.ELEMENT_NOT_VISIBLE:
             raise errors.ElementNotVisibleException(message=message, status=status, stacktrace=stacktrace)
+        elif status == errors.ErrorCodes.ELEMENT_NOT_ACCESSIBLE:
+            raise errors.ElementNotAccessibleException(message=message, status=status, stacktrace=stacktrace)
         elif status == errors.ErrorCodes.INVALID_ELEMENT_STATE:
             raise errors.InvalidElementStateException(message=message, status=status, stacktrace=stacktrace)
         elif status == errors.ErrorCodes.UNKNOWN_ERROR:
diff --git a/testing/marionette/client/marionette/tests/unit/test_accessibility.py b/testing/marionette/client/marionette/tests/unit/test_accessibility.py
new file mode 100644
index 000000000000..1326181dc07e
--- /dev/null
+++ b/testing/marionette/client/marionette/tests/unit/test_accessibility.py
@@ -0,0 +1,86 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from marionette_test import MarionetteTestCase
+from errors import ElementNotAccessibleException
+from errors import ElementNotVisibleException
+
+
+class TestAccessibility(MarionetteTestCase):
+
+    # Elements that are accessible with and without the accessibliity API
+    valid_elementIDs = [
+        # Button1 is an accessible button with a valid accessible name
+        # computed from subtree
+        "button1",
+        # Button2 is an accessible button with a valid accessible name
+        # computed from aria-label
+        "button2"
+    ]
+
+    # Elements that are not accessible with the accessibility API
+    invalid_elementIDs = [
+        # Button3 does not have an accessible object
+        "button3",
+        # Button4 does not support any accessible actions
+        "button4",
+        # Button5 does not have a correct accessibility role and may not be
+        # manipulated via the accessibility API
+        "button5",
+        # Button6 is missing an accesible name
+        "button6",
+        # Button7 is not currently visible via the accessibility API and may
+        # not be manipulated by it
+        "button7",
+        # Button8 is not currently visible via the accessibility API and may
+        # not be manipulated by it (in hidden subtree)
+        "button8"
+    ]
+
+    # Elements that are either accessible to accessibility API or not accessible
+    # at all
+    falsy_elements = [
+        # Element is only visible to the accessibility API and may be
+        # manipulated by it
+        "button9",
+        # Element is not currently visible
+        "button10"
+    ]
+
+    def run_element_test(self, ids, testFn):
+        for id in ids:
+            element = self.marionette.find_element("id", id)
+            testFn(element)
+
+    def setup_accessibility(self, raisesAccessibilityExceptions=True, navigate=True):
+        self.marionette.delete_session()
+        self.marionette.start_session(
+            {"raisesAccessibilityExceptions": raisesAccessibilityExceptions})
+        # Navigate to test_accessibility.html
+        if navigate:
+            test_accessibility = self.marionette.absolute_url("test_accessibility.html")
+            self.marionette.navigate(test_accessibility)
+
+    def test_valid_single_tap(self):
+        self.setup_accessibility()
+        # No exception should be raised
+        self.run_element_test(self.valid_elementIDs, lambda button: button.tap())
+
+    def test_invalid_single_tap(self):
+        self.setup_accessibility()
+        self.run_element_test(self.invalid_elementIDs,
+                              lambda button: self.assertRaises(ElementNotAccessibleException,
+                                                               button.tap))
+        self.run_element_test(self.falsy_elements,
+                              lambda button: self.assertRaises(ElementNotAccessibleException,
+                                                               button.tap))
+
+    def test_invalid_single_tap_no_exceptions(self):
+        self.setup_accessibility(False, True)
+        # No exception should be raised
+        self.run_element_test(self.invalid_elementIDs, lambda button: button.tap())
+        # Elements are invisible
+        self.run_element_test(self.falsy_elements,
+                              lambda button: self.assertRaises(ElementNotVisibleException,
+                                                               button.tap))
diff --git a/testing/marionette/client/marionette/tests/unit/unit-tests.ini b/testing/marionette/client/marionette/tests/unit/unit-tests.ini
index 149c5dd450d2..e47ac7bbea75 100644
--- a/testing/marionette/client/marionette/tests/unit/unit-tests.ini
+++ b/testing/marionette/client/marionette/tests/unit/unit-tests.ini
@@ -16,6 +16,8 @@ skip = false
 [test_session.py]
 [test_capabilities.py]
 
+[test_accessibility.py]
+
 [test_expectedfail.py]
 expected = fail
 [test_import_script.py]
diff --git a/testing/marionette/client/marionette/www/test_accessibility.html b/testing/marionette/client/marionette/www/test_accessibility.html
new file mode 100644
index 000000000000..c91be89819b8
--- /dev/null
+++ b/testing/marionette/client/marionette/www/test_accessibility.html
@@ -0,0 +1,38 @@
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+
+<!DOCTYPE html>
+
+<html>
+<meta charset="UTF-8">
+<head>
+<title>Marionette Test</title>
+</head>
+<body>
+  <button id="button1">button1</button>
+  <button id="button2" aria-label="button2"></button>
+  <span id="button3">I am a bad button with no accessible</span>
+  <h1 id="button4">I am a bad button that is actually a header</h1>
+  <h1 id="button5">
+    I am a bad button that is actually an actionable header with a listener
+  </h1>
+  <button id="button6"></button>
+  <button id="button7" aria-hidden="true">button7</button>
+  <div aria-hidden="true">
+    <button id="button8">button8</button>
+  </div>
+  <button id="button9" style="position:absolute;left:-100px;top:-455px;">
+    button9
+  </button>
+  <button id="button10" style="visibility:hidden;">
+    button10
+  </button>
+  <script>
+      document.getElementById('button5').addEventListener('click', function() {
+        // A pseudo button that has a listener but is missing button semantics.
+        return true;
+      });
+  </script>
+</body>
+</html>
diff --git a/testing/marionette/marionette-elements.js b/testing/marionette/marionette-elements.js
index 323466bbf310..1f0281d12f6a 100644
--- a/testing/marionette/marionette-elements.js
+++ b/testing/marionette/marionette-elements.js
@@ -12,6 +12,7 @@
  */
 
 this.EXPORTED_SYMBOLS = [
+  "Accessibility",
   "ElementManager",
   "CLASS_NAME",
   "SELECTOR",
@@ -47,6 +48,127 @@ function ElementException(msg, num, stack) {
   this.stack = stack;
 }
 
+this.Accessibility = function Accessibility() {
+  // A flag indicating whether the accessibility issue should be logged or cause
+  // an exception. Default: log to stdout.
+  this.strict = false;
+  this.accessibleRetrieval = Components.classes[
+    '@mozilla.org/accessibleRetrieval;1'].getService(
+      Components.interfaces.nsIAccessibleRetrieval);
+};
+
+Accessibility.prototype = {
+  /**
+   * Accessible object roles that support some action
+   * @type Object
+   */
+  actionableRoles: new Set([
+    'pushbutton',
+    'checkbutton',
+    'combobox',
+    'key',
+    'link',
+    'menuitem',
+    'check menu item',
+    'radio menu item',
+    'option',
+    'radiobutton',
+    'slider',
+    'spinbutton',
+    'pagetab',
+    'entry',
+    'outlineitem'
+  ]),
+
+  /**
+   * Get an accessible object for a DOM element
+   * @param nsIDOMElement element
+   * @param Boolean mustHaveAccessible a flag indicating that the element must
+   * have an accessible object
+   * @return nsIAccessible object for the element
+   */
+  getAccessibleObject(element, mustHaveAccessible = false) {
+    let acc = this.accessibleRetrieval.getAccessibleFor(element);
+    if (!acc && mustHaveAccessible) {
+      this.handleErrorMessage('Element does not have an accessible object');
+    }
+    return acc;
+  },
+
+  /**
+   * Check if the accessible has a role that supports some action
+   * @param nsIAccessible object
+   * @return Boolean an indicator of role being actionable
+   */
+  isActionableRole(accessible) {
+    return this.actionableRoles.has(
+      this.accessibleRetrieval.getStringRole(accessible.role));
+  },
+
+  /**
+   * Determine if an accessible has at least one action that it supports
+   * @param nsIAccessible object
+   * @return Boolean an indicator of supporting at least one accessible action
+   */
+  hasActionCount(accessible) {
+    return accessible.actionCount > 0;
+  },
+
+  /**
+   * Determine if an accessible has a valid name
+   * @param nsIAccessible object
+   * @return Boolean an indicator that the element has a non empty valid name
+   */
+  hasValidName(accessible) {
+    return accessible.name && accessible.name.trim();
+  },
+
+  /**
+   * Check if an accessible has a set hidden attribute
+   * @param nsIAccessible object
+   * @return Boolean an indicator that the element has a hidden accessible
+   * attribute set to true
+   */
+  hasHiddenAttribute(accessible) {
+    let hidden;
+    try {
+      hidden = accessible.attributes.getStringProperty('hidden');
+    } finally {
+      // If the property is missing, exception will be thrown.
+      return hidden && hidden === 'true';
+    }
+  },
+
+  /**
+   * Check if an accessible is hidden from the user of the accessibility API
+   * @param nsIAccessible object
+   * @return Boolean an indicator that the element is hidden from the user
+   */
+  isHidden(accessible) {
+    while (accessible) {
+      if (this.hasHiddenAttribute(accessible)) {
+        return true;
+      }
+      accessible = accessible.parent;
+    }
+    return false;
+  },
+
+  /**
+   * Send an error message or log the error message in the log
+   * @param String message
+   */
+  handleErrorMessage(message) {
+    if (!message) {
+      return;
+    }
+    if (this.strict) {
+      throw new ElementException(message, 56, null);
+    }
+    dump(Date.now() + " Marionette: " + message);
+  }
+};
+
 this.ElementManager = function ElementManager(notSupported) {
   this.seenItems = {};
   this.timer = Components.classes["@mozilla.org/timer;1"].createInstance(Components.interfaces.nsITimer);
diff --git a/testing/marionette/marionette-listener.js b/testing/marionette/marionette-listener.js
index 926ee2a3fe4c..4e2ad8318fce 100644
--- a/testing/marionette/marionette-listener.js
+++ b/testing/marionette/marionette-listener.js
@@ -39,6 +39,7 @@ let listenerId = null; //unique ID of this listener
 let curFrame = content;
 let previousFrame = null;
 let elementManager = new ElementManager([]);
+let accessibility = new Accessibility();
 let importedScripts = null;
 let inputSource = null;
 
@@ -210,6 +211,7 @@ function waitForReady() {
  */
 function newSession(msg) {
   isB2G = msg.json.B2G;
+  accessibility.strict = msg.json.raisesAccessibilityExceptions;
   resetValues();
   if (isB2G) {
     readyStateTimer.initWithCallback(waitForReady, 100, Ci.nsITimer.TYPE_ONE_SHOT);
@@ -945,11 +947,15 @@ function singleTap(msg) {
   let command_id = msg.json.command_id;
   try {
     let el = elementManager.getKnownElement(msg.json.id, curFrame);
+    let acc = accessibility.getAccessibleObject(el, true);
     // after this block, the element will be scrolled into view
-    if (!checkVisible(el, msg.json.corx, msg.json.cory)) {
-       sendError("Element is not currently visible and may not be manipulated", 11, null, command_id);
-       return;
+    let visible = checkVisible(el, msg.json.corx, msg.json.cory);
+    checkVisibleAccessibility(acc, visible);
+    if (!visible) {
+      sendError("Element is not currently visible and may not be manipulated", 11, null, command_id);
+      return;
     }
+    checkActionableAccessibility(acc);
     if (!curFrame.document.createTouch) {
       mouseEventsOnly = true;
     }
@@ -962,6 +968,48 @@ function singleTap(msg) {
   }
 }
 
+/**
+ * Check if the element's visible state corresponds to its accessibility API
+ * visibility
+ * @param nsIAccessible object
+ * @param Boolean visible element's visibility state
+ */
+function checkVisibleAccessibility(accesible, visible) {
+  if (!accesible) {
+    return;
+  }
+  let hiddenAccessibility = accessibility.isHidden(accesible);
+  let message;
+  if (visible && hiddenAccessibility) {
+    message = 'Element is not currently visible via the accessibility API ' +
+      'and may not be manipulated by it';
+  } else if (!visible && !hiddenAccessibility) {
+    message = 'Element is currently only visible via the accessibility API ' +
+      'and can be manipulated by it';
+  }
+  accessibility.handleErrorMessage(message);
+}
+
+/**
+ * Check if it is possible to activate an element with the accessibility API
+ * @param nsIAccessible object
+ */
+function checkActionableAccessibility(accesible) {
+  if (!accesible) {
+    return;
+  }
+  let message;
+  if (!accessibility.hasActionCount(accesible)) {
+    message = 'Element does not support any accessible actions';
+  } else if (!accessibility.isActionableRole(accesible)) {
+    message = 'Element does not have a correct accessibility role ' +
+      'and may not be manipulated via the accessibility API';
+  } else if (!accessibility.hasValidName(accesible)) {
+    message = 'Element is missing an accesible name';
+  }
+  accessibility.handleErrorMessage(message);
+}
+
 /**
  * Given an element and a pair of coordinates, returns an array of the form
  * [ clientX, clientY, pageX, pageY, screenX, screenY ]
diff --git a/testing/marionette/marionette-server.js b/testing/marionette/marionette-server.js
index 5bb98fa334d5..0d479af522b6 100644
--- a/testing/marionette/marionette-server.js
+++ b/testing/marionette/marionette-server.js
@@ -174,6 +174,7 @@ function MarionetteServerConnection(aPrefix, aTransport, aServer)
     // Supported features
     "handlesAlerts": false,
     "nativeEvents": false,
+    "raisesAccessibilityExceptions": false,
     "rotatable": appName == "B2G",
     "secureSsl": false,
     "takesElementScreenshot": true,
@@ -2899,8 +2900,10 @@ MarionetteServerConnection.prototype = {
         this.curBrowser.elementManager.seenItems[reg.id] = Cu.getWeakReference(listenerWindow);
         if (nullPrevious && (this.curBrowser.curFrameId != null)) {
           if (!this.sendAsync("newSession",
-                              { B2G: (appName == "B2G") },
-                              this.newSessionCommandId)) {
+              { B2G: (appName == "B2G"),
+                raisesAccessibilityExceptions:
+                  this.sessionCapabilities.raisesAccessibilityExceptions },
+              this.newSessionCommandId)) {
             return;
           }
           if (this.curBrowser.newSession) {