diff --git a/README.md b/README.md
index bacddd04..2c9bc0da 100644
--- a/README.md
+++ b/README.md
@@ -189,6 +189,7 @@ Method                                             | Description
 -------------------------------------------------- | ------------------------------------------------------------------
 `keyExists($array, $key, $message = '')`           | Check that a key exists in an array
 `keyNotExists($array, $key, $message = '')`        | Check that a key does not exist in an array
+`validArrayKey($key, $message = '')`               | Check that a value is a valid array key (int or string)
 `count($array, $number, $message = '')`            | Check that an array contains a specific number of elements
 `minCount($array, $min, $message = '')`            | Check that an array contains at least a certain number of elements
 `maxCount($array, $max, $message = '')`            | Check that an array contains at most a certain number of elements
diff --git a/src/Assert.php b/src/Assert.php
index 4c9a334f..ee15dff3 100644
--- a/src/Assert.php
+++ b/src/Assert.php
@@ -95,6 +95,7 @@
  * @method static void nullOrMethodNotExists($value, $method, $message = '')
  * @method static void nullOrKeyExists($value, $key, $message = '')
  * @method static void nullOrKeyNotExists($value, $key, $message = '')
+ * @method static void nullOrValidArrayKey($value, $message = '')
  * @method static void nullOrCount($value, $key, $message = '')
  * @method static void nullOrMinCount($value, $min, $message = '')
  * @method static void nullOrMaxCount($value, $max, $message = '')
@@ -177,6 +178,7 @@
  * @method static void allMethodNotExists($values, $method, $message = '')
  * @method static void allKeyExists($values, $key, $message = '')
  * @method static void allKeyNotExists($values, $key, $message = '')
+ * @method static void allValidArrayKey($values, $message = '')
  * @method static void allCount($values, $key, $message = '')
  * @method static void allMinCount($values, $min, $message = '')
  * @method static void allMaxCount($values, $max, $message = '')
@@ -1602,6 +1604,24 @@ public static function keyNotExists($array, $key, $message = '')
         }
     }
 
+    /**
+     * Checks if a value is a valid array key (int or string).
+     *
+     * @param mixed  $key
+     * @param string $message
+     *
+     * @throws InvalidArgumentException
+     */
+    public static function validArrayKey($value, $message = '')
+    {
+        if (!(\is_int($value) || \is_string($value))) {
+            static::reportInvalidArgument(\sprintf(
+                $message ?: 'Expected string or integer. Got: %s',
+                static::typeToString($value)
+            ));
+        }
+    }
+
     /**
      * Does not check if $array is countable, this can generate a warning on php versions after 7.2.
      *
diff --git a/tests/AssertTest.php b/tests/AssertTest.php
index 4546dab5..890475d5 100644
--- a/tests/AssertTest.php
+++ b/tests/AssertTest.php
@@ -403,6 +403,13 @@ public function getTests()
             array('keyNotExists', array(array('key' => 0), 'key'), false),
             array('keyNotExists', array(array('key' => null), 'key'), false),
             array('keyNotExists', array(array('key' => null), 'foo'), true),
+            array('validArrayKey', array('abcd'), true),
+            array('validArrayKey', array(1), true),
+            array('validArrayKey', array(false), false),
+            array('validArrayKey', array(true), false),
+            array('validArrayKey', array(new stdClass()), false),
+            array('validArrayKey', array(new ToStringClass('testString')), false),
+            array('validArrayKey', array(self::getResource()), false),
             array('count', array(array(0, 1, 2), 3), true),
             array('count', array(array(0, 1, 2), 2), false),
             array('minCount', array(array(0), 2), false),