The interest in the field of Mobile Ad hoc Network (MANET) is growing since last few years because of its practical applications in mobile devices. MANET is particularly vulnerable to security attacks in comparison to wired network or infrastructure-based wireless network due to its fundamental characteristics such as the open medium, dynamic network topology, autonomous terminal, lack of centralized monitoring and management. In order to provide secure and good communication and transmission, researchers have worked specifically on the security issues in MANETs and many secure routing protocols and security measures were proposed. The black hole attack is one of the most prominent security threats which disrupt the routing in Mobile Networks. The scope of this work is to understand the effects of Black hole attack in MANET and devise a strategy to mitigate the attack for Ad-Hoc on Demand Distance Vector (AODV) Routing Protocol in MANETs.