Routing attacks have been identified for single path routing in wireless ad hoc networks. The effects of routing attacks on multipath routing have not been addressed so far. In this paper, an approach have been proposed to mitigate the black hole attack using AOMDV (Ad hoc On demand Multipath Distance Vector) routing protocol. Some improvements have been made in AOMDV protocol. These improvements make the protocol robust against black hole attack along multipath route discovery process. The performance of proposed approach has been investigated to further reduce the overhead as described in this paper.