A mobile ad hoc network (MANET) is considered as an autonomous network, which consists of mobile nodes, which communicate with each other over wireless links. When there is no fixed infrastructure, nodes have to cooperate in order to incorporate the necessary network functionality. Ad hoc on Demand Distance Vector (AODV) protocol is one of the primary principal routing protocols implemented in Ad hoc networks. The security of the AODV protocol is threaded by a specific kind of attack called ‘Black Hole’ attack. This paper presents a technique to prevent the Black hole attack by implementing negotiation with neighbors who claim to maintain a route to destination. Negotiation process is strengthen by apriori method to judge about suspicious node. Apriori algorithm is an effective association rule mining method with relatively low complexity, which is proper for MANETs. To achieve more improvement, fuzzy version of ADOV is used. The simulation results indicate that the proposed protocol provides more securable routing and also more efficiency in terms of packet delivery, overhead and detection rate than the conventional AODV and fuzzy AODV in the presence of Black hole attacks.