4Recent rapid penetration of Internet of Things (IoT) in various fields such as smart homes, healthcare, and industrial applications has raised new challenges on the QoS requirements including data prioritization and energy saving. In IoT networks, data is heterogeneous and varies in a wide range of categories and urgency. More critical data must be served more quickly and reliably than regular data. In order to deal with crucial issues effectively and improve the performance of wireless sensor networks in IoT, we propose an efficient Backoff Priority-based Medium Access Control (BoP-MAC) scheme that supports multiple priority data and exploits the use of backoff mechanism. In our proposed solution, data priority is utilized to properly resize the backoff window at the MAC layer to ensure that high-priority data are transferred earlier and more reliably. Numerical simulations are used on OMNeT++ to verify the efficiency of our proposed BoP-MAC protocol in comparison with that of a notably conventional MAC protocol called Timeout Multi-priority-based MAC (TMPQ-MAC) protocol. The attained experimental results demonstrate that our developed BoP-MAC protocol outperforms the comparable conventional one and becomes more efficient for large-scale wireless sensor networks. It can effectively cope with various data priorities and enhance significantly the overall performance, in terms of latency, energy consumption, and packet success ratio, of the network. Index Terms4Backoff window, Internet of things, MAC protocol, Wireless sensor networks.