A mobile ad hoc network (MANET) is a collection of wireless nodes, which works well only if those mobile nodes are good and behave cooperatively. The lack of infrastructure support and resource constraint is the key issue that causes dishonest and non-cooperative nodes. Therefore, MANET is vulnerable to serious attacks. To reduce the hazards from such nodes and enhance the security of the network, this paper extends an Ad hoc On-Demand Multipath Distance Vector (AOMDV) Routing protocol, named as Trust-based Secured Adhoc On-demand Multipath Distance Vector (TS-AOMDV), which is based on the nodes' routing behavior. The proposed TSAOMDV aims at identifying and isolating the attacks such as flooding, black hole, and gray hole attacks in MANET. With the help of Intrusion Detection System (IDS) and trust-based routing, attack identification and isolation are carried out in two phases ofrouting such as route discovery and data forwarding phase. IDS facilitates complete routing security by observing both control packets and data packets that are involved in the route identification and the data forwarding phases. To improve the routing performance, the IDS integrates the measured statistics into the AOMDV routing protocol for the detection of attackers. This facilitates the TS-AOMDV to provide better routing performance and security in MANET. Finally, the Trust based Secured AOMDV, TS-AOMDV is compared with the existing AOMDV through the NS2 based simulation model. The performance evaluation reveals that the proposed TS-AOMDV improves the performance in terms of throughput by 57.1% more than that of an AOMDV under adversary scenario. The simulated results show that the TS-AOMDV outperforms the AOMDV routing protocol.