diff --git a/README.md b/README.md
index dd16a1422..6ad47e161 100644
--- a/README.md
+++ b/README.md
@@ -41,10 +41,10 @@ object:
 ```php
 use \jamesiarmes\PhpEws\Client;
 
-$ews = new Client($server, $username, $password, $version);
+$ews = new Client($server, $username, $password, $version, $client_certificate);
 ```
 
-The `Client` class takes four parameters for its constructor:
+The `Client` class takes five parameters for its constructor:
 
 * `$server`: The url to the exchange server you wish to connect to, without
   the protocol. Example: mail.example.com. If you have trouble determining the
@@ -56,6 +56,8 @@ The `Client` class takes four parameters for its constructor:
 * `$version` (optional): The version of the Exchange sever to connect to. Valid
   values can be found at `\jamesiarmes\PhpEws\Client::VERSION_*`. Defaults to
   Exchange 2007.
+* `$client_certicaticate` (optional): The path to the client certificate to use
+  for authentication. When specified, `$username` and `$password` are ignored.
 
 Once you have your `\jamesiarmes\PhpEws\Client` object, you need to build your
 request object. The type of object depends on the operation you are calling. If
diff --git a/src/Client.php b/src/Client.php
index c552d1009..af6c6e83b 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -152,6 +152,11 @@ class Client
      */
     protected $version;
 
+    /**
+     * @var ?string Path to client certificate
+     */
+    protected $client_certificate;
+
     /**
      * Constructor for the ExchangeWebServices class
      *
@@ -165,7 +170,8 @@ public function __construct(
         $server = null,
         $username = null,
         $password = null,
-        $version = self::VERSION_2013
+        $version = self::VERSION_2013,
+        $client_certificate = null
     ) {
         // Set the object properties.
         $this->setServer($server);
@@ -189,6 +195,16 @@ public function getClient()
         return $this->soap;
     }
 
+    /**
+     * Gets the client certificate path (or null if not set)
+     *
+     * @return string|null
+     */
+    public function getClientCertificate()
+    {
+        return $this->client_certificate;
+    }
+
     /**
      * Sets the cURL options that will be set on the SOAP client.
      *
@@ -280,6 +296,22 @@ public function setVersion($version)
         $this->headers = array();
     }
 
+    /**
+     * Sets the client certificate. Should be a readable path to a certificate file
+     *
+     * @param string $client_certificate
+     *
+     * @throws \InvalidArgumentException  If the certificate is not readable
+     */
+    public function setClientCertificate($client_certificate)
+    {
+        if (!is_readable($client_certificate)) {
+            throw new \InvalidArgumentException('Client certificate not readable');
+        }
+
+        $this->client_certificate = $client_certificate;
+    }
+
     /**
      * Adds one or more delegates to a principal's mailbox and sets specific
      * access permissions.
@@ -1604,16 +1636,25 @@ public function UploadItems($request)
      */
     protected function initializeSoapClient()
     {
+        $options = array(
+                         'location' => 'https://' . $this->server . '/EWS/Exchange.asmx',
+                         'classmap' => $this->classMap(),
+                         'curlopts' => $this->curl_options,
+                         'features' => SOAP_SINGLE_ELEMENT_ARRAYS
+        );
+
+        //If client certificate is set, add it to the options for usage
+        //Else, default to login/password
+        if ($this->client_certificate !== null) {
+            $options['local_cert'] = $this->client_certificate;
+        } else {
+            $options['user'] = $this->username;
+            $options['password'] = $this->password;
+        }
+
         $this->soap = new SoapClient(
             dirname(__FILE__) . '/assets/services.wsdl',
-            array(
-                'user' => $this->username,
-                'password' => $this->password,
-                'location' => 'https://' . $this->server . '/EWS/Exchange.asmx',
-                'classmap' => $this->classMap(),
-                'curlopts' => $this->curl_options,
-                'features' => SOAP_SINGLE_ELEMENT_ARRAYS,
-            )
+            $options
         );
 
         return $this->soap;