Wireless Sensor Networks (WSNs) is a distributed collection of tiny wireless nodes which forms an ad hoc network dynamically to sense the natural phenomenon and sent it to the control station. Due to the resource constrained nature of WSN, maximizing the nodes life time is main and challenging issue. In this paper, Fitness Function based Routing Protocol (FFBRP) is proposed which provides the optimal routing to increase the life time of nodes in a network. The proposed protocol selects the fitness functions based on the important routing parameters like nodes energy consumption, nodes life time, packet Delivery ratio of nodes, distance between nodes, end to end delay of nodes and routing overhead of nodes. Based on the combination of selected fitness function parameters, the intelligent rules are generated and the optimal routes are discovered to perform energy efficient effective routing in WSN. By doing so, the proposed protocol provides better performance in terms of network life time and has better Quality of Service (QoS) than other existing techniques. The implementation of the proposed scheme is carried out using Network Simulator (NS2) with mannasim framework. Simulation results justifies that, proposed protocol outperforms the existing techniques and has better Packet Delivery Ratio, throughput, network life time, energy consumption, end to end delay and routing overhead. © 2019, Blue Eyes Intelligence Engineering and Sciences Publication. All rights reserved.