In this paper Dynamic Sleep Scheduling (DSS) for Minimizing Delay in Wireless Sensor Network is proposed. To reduce delay, DSS identifies nodes for different sleep/wake according to their traffic load at two levels: a) Nodes with different sleep/wake schedule requirement according to their different traffic load based on their topological importance in the network. b) Nodes with different sleep/wake schedule based on handling burst traffic in the proximity of event occurrence node. It then assign different active interval to the nodes, according to their variable traffic load requirement defined by node topological importance and by handling burst traffic in the proximity of event occurrence node. Using these heuristics DSS reduces end-to-end delay and minimize energy per packet by minimizing the congestion at nodes having heavy traffic load. Simulations are carried out to evaluate the performance of the proposed protocol, by comparing its performance with S-MAC and anycast protocols. Simulation results demonstrated that the proposed protocol has significantly reduced the end-to-end delay, as well as has improved average energy per packet. © 2011 IEEE.