We propose a novel context detection mechanism in Wireless Sensor Networks, called PROCON. In PROCON, context decisions are made in a distributed way, by cooperation of nodes connected through a context overlay on the network. As a result, the sensor network can deliver context level information, not low level sensing data, directly to proper actuators. Moreover, PROCON achieves highly efficient energy consumption compared to the existing centralized context detection mechanism. The analysis and simulation results show that the proposed mechanism outperforms the existing centralized mechanism in average energy consumption, capability of mitigating congestion to a base station, context service lifetime, and reliability.