Mobile ad hoc networks consist of mobile nodes. These nodes do not follow any particular topology. Transmitting data on these mobile nodes is a challenging task especially when the network size grows rapidly. In this situation, congestion problem occurs which degrades the performance of the overall network. Many algorithms are proposed to control the congestion, but still there is no universally accepted approach which can minimize the congestion. In this paper, a fuzzy based congestion control mechanism is designed. The performance of the proposed scheme is evaluated on qualnet which is a successor of glomosim.