Abstract: User authentication is the core element which offers authentication, authorization and accounting in cloud computing environments for cloud users. In recent years, so, many authentication schemes for cloud computing has been introduced. Either the authentication scheme involves security problems or cannot be implemented in the cloud computing environment. The proposed system, TPUA that is Two Phase User Authentication mechanism using ID is easily adapted to a cloud computing environment and deals with the security problems spotted in related authentication schemes. It involves user authentication which provides complete mutual authentication with data protection. When compared to other user authentication schemes the proposed system has higher security and minimal computational costs.