Improved methods and systems for integrating client-side single sign-on (SSO) authentication security infrastructure with a mobile authorization protocol are disclosed that provide clients with secured SSO mobile access to third-party services. Embodiments of the present invention leverage SSO authentication protocols that are utilized at many client-side systems already and integrate these SSO authentication protocols with a mobile SSO authorization protocol, thereby effectively extending the SSO framework to mobile service requests of web services at third-party service provider systems. Embodiments of the present invention provide a secure and automated solution which may be implemented in any existing client-side SSO frameworks with minimum cost and time, while providing a lightweight and secure solution that provides users using either native applications or mobile web application to access third-party web services.