The deployment of sensor networks for security and safety related environments requires securing communication primitives such as broadcast, multicast and point to point communication. Recent research shows that multicast provides high energy saving in IP supported wireless sensor networks (WSN). In this work, we investigate how to secure route discovery of the Multicast Ad-hoc on Demand Distance Vector (MAODV) protocol for WSNs. For the ad-hoc networks ARIADNE, SEAD, ARAN are some of the solutions, which cannot be directly applied to energy constrained WSNs. Here, we propose a secure route discovery of MAODV based on TESLA and one-way hash function. We have simulated our work using NS-2. The performance of the secured MAODV and the unsecured MAODV is compared.