Abstract-In wireless sensor network (WSN), energy and packet forwarding tendencies of sensor nodes plays a potential role in ensuring a maximum degree of co-operation under data delivery.This quantified level of co-operation represents the performance of the network in terms of increased packet delivery rate, throughput and decreased level of control overhead and delay depending on the data being aggregated. The performance of a sensor network is highly influenced by the selfish behaving nature of sensor nodes that gets exhibited when the residual energy reaches below a tolerable level of activeness in packet forwarding. The selfish sensor node needs to be identified in future through reliable forecasting mechanism for improving the lifetime and packet delivery rate. Semi-Markov Process Inspired Selfish-aware Co-operative Scheme for WSNs (SMPISCS) is propounded for making an attempt to mitigate selfish nodes for prolonging the lifetime of the network and balancing energy consumptions of the network. In SMPISCS model possible kinds of sensor node's behavior for quantifying and future forecasting the probability with which the node could turn into selfish. Simulation experiments are carried out through ns-2 and the performance of the network are analyzed based on varying number of sensor nodes, number of selfish sensor nodes and range of detection threshold.