Impact of selfish nodes in multicast Ad hoc on demand Distance Vector Protocol Mobile ad hoc network (MANET ) is a dynamically reconfigurable mobile wireless network that does not have a fixed infrastructure. The network topology of MANETs changes very fast, making it more difficult to find the routes and provide security for the messages packets used. Since MANETs are useful in disaster operations, military operation, the need for the group communication is vital. Most of the multicast protocol proposed for ad hoc networks assume a trusted, non-adversial environment and do not take security issues into account in their design. But in real time a MANET is vulnerable to attacks than a wired or infrastructure wireless network. This thesis investigates the security of Multicast Ad-hoc on demand distance vector protocol (MAODV), a well known multicast routing protocol in MANET by identifying the impact of selfish nodes on it. Though there exists many security extensions on MADOV, the selfish behaviour of nodes have not been explored extensively. Thus, a security extension to address the selfish node attack in multicast routing has been proposed in this project. The solution proposed is incorporated in MAODV protocol and analyzed in a simulation environment using NS-2simulator.