WiMAX is a promising technology that provides high data throughput with low delays for various user types and modes of operation. These advantages make WiMAX applicable both for infrastructure purposes and end-client usage. Since WiMAX is presented as a network framework and a last-mile technology, it is believed to be capable of handling a wide range of usage scenarios. For example, while the end users have an opportunity to use WiMAX as the primary connection medium for acquiring services such as on-demand video streaming, VoIP connections and mobile bank transactions, the service providers may use it for data relaying purposes among access points. To meet the technical requirements of these various scenarios, majority of the WiMAX research has been conducted on physical and MAC layers; however little has been invested in a comprehensive and efficient security solution, which has resulted in a wide range of security weaknesses and reactive solutions. Many security problems remain to be addressed in different modes and for different user types even in the final security standard of WiMAX, PKMv2. Mobile multi-hop relay (MMR) WiMAX networks have attracted lots of interest in wireless communication industry because of its scalable coverage, improved data rate and relatively low cost. Even with the additional security functionalities security of MMR WiMAX network is the main challenge because messages have to be transmitted through one or more relay stations, which makes it more difficult to ensure the authenticity of messages and entities involved in the transmission. In this thesis, we present a hybrid security solution to overcome the security problem of rogue station (BS/RS) attack and denial of service attack (DoS) in MMR WiMAX.