Abstract: This paper proposes a novel heterogeneous relaying scheme that enhances network lifetime for two-hop wireless sensor networks (WSNs). Relaying is a spatial diversity technique which can achieve high energy-efficiency; hence it has become an attractive approach for lifetime extension in wireless networks. In this study, relay nodes are deployed heterogeneously either amplify-and-forward (AF) or decode-and-forward (DF) protocol between a source and a destination. By estimating channel gain and residual energy of relay nodes, the source node can determine the best assistant relay to retransmit failure packets to the destination. As a result, relay nodes can keep the balance of energy dissipation and extending the network lifetime. Numerical evaluations show that the proposed scheme is fully effective in terms of the energy conservation for WSNs.