Recently, wireless sensor networks (WSNs) have been used increasingly in military and civilian fields, especially for target tracking and environmental monitoring purposes. The main obstacle in the way of broader use of WSNs is the limited charge of sensors used in these networks. Research has shown that the power consumption of these sensors can be reduced through the sensible use of routing protocols and multi-hop communications. While cluster-based multi-hop protocols have shown to be very effective in reducing power consumption of sensors, they tend to suffer from power balance and data conflict problems. This paper applied the multi-objective whale optimization algorithm to develop a cluster-based routing protocol for WSNs. For improving the time division multiple access cycle, a bottom-up continuous time slot allocation scheme was used with the purpose of preventing data collision in multi-hop communications, as well as maximizing the sleep period of all idle nodes, including the cluster heads. Simulations performed in MATLAB demonstrated the ability of the developed protocol in prolonging the network lifespan by almost 100% by balancing the power consumption of its sensors.