Wireless Sensor Networks (WSNs) have gained significant attention due to their wide range of applications. In these networks, the sensor nodes collect different types of data from the surrounding environment. There are many applications that require sensor node to transmit urgent data packets faster than normal data packets. In the literature, most of the available medium access control (MAC) protocols have not considered quality-of-service (QoS) and have not addressed multi-priority of the data packets. In this paper, a multi-priority based MAC protocol is proposed, which provides QoS in WSNs, called MPQ-MAC protocol. In the MPQ-MAC protocol, a novel technique is proposed to reduce the delay and energy consumption in the network. Furthermore, the performance of the MPQ-MAC protocol has been evaluated in terms of average delay for priority data packets, energy consumption per node, packet delay, network throughput and packet delivery ratio using Castalia simulator. Simulation results show that the proposed protocol reduces the delay for priority data packet of up to 46.5 and energy consumption per node of up to 1.7 while maintaining network throughput and packet delivery ratio in the network. © 2017 IEEE.