In wireless sensor networks (WSNs), energy harvesting techniques have emerged as a promising solution to overcome the energy challenge. In certain applications, sensor nodes are required to transmit higher priority data packets with minimum delay. In the literature, most of the available protocols in energy harvesting WSNs (EH-WSNs) did not support the priority of data packets. In addition, these protocols have not considered different energy levels of the receiver and have also not been tested under real-world energy harvesting rates. Therefore, there is a need to design a medium access control (MAC) protocol for Quality-of-Service (QoS) in EH-WSNs, which can support the priority of data packets and consider different energy levels of the receiver with realistic harvesting rates. This paper proposes a QoS MAC protocol for Prioritized Data in EH-WSNs (QPPD-MAC). The QPPD-MAC supports multi-priority of data packets and uses a novel technique to shorten the delay by cancelling the waiting timer for the highest priority data packets. Furthermore, it adjusts the receiver duty cycle according to its current energy level under dynamic energy harvesting conditions to improve performance. The QPPD-MAC protocol is evaluated under a more realistic scenario using high resolution real empirical solar irradiance data and its performance compared with QAEE-MAC and ERI-MAC. The results show that the QPPD-MAC gives an impressive reduction of more than 54 in the average end-to-end delay of priority data packets in both high and low irradiance scenarios. Moreover, in the low solar irradiance, it shows an improvement in the packet delivery ratio of up to 10 and gives better performance in terms of network throughput and energy consumption per bit. © 2018 Elsevier B.V.