Abstract The MAC layer of the IEEE 802.11 standard deploys a CSMA/CA protocol to regulate the access to the shared medium. Not only other IEEE 802.11 stations but also non-IEEE 802.11 devices can be a source of interference, causing collisions and, therefore, re-transmissions, leading to an increased packet latency and a decrease of throughput. As in general, the non-IEEE 802.11 devices do not employ the IEEE8 802.11 CSMA/CA protocol (in particular carrier sensing and the behavior when the medium is sensed busy), the impact of the interference they cause may lead to vital performance degradation of the IEEE 802.11 network. This impact of non-IEEE 802.11 interfering sources on the network performance has not been accurately modeled yet in literature. In this paper, we first characterize a non-IEEE 802.11 interfering source by employing an on-off process. Then we propose, based on earlier results from Bianchi, an analytical model to predict latency and throughput in a saturated as well as an unsaturated network, considering that an interfering source is present. The model utilizes a Markov chain to correctly characterize the behavior of the back-off algorithm of a tagged station in the presence of an interfering source, as well as a Quasi Birth-Death (QBD) process to model the station’s packet queue behavior. We show that we can accurately estimate the impact of non-IEEE 802.11 inference on IEEE 802.11 performance. The model is validated through a comparison with measurements in a real IEEE 802.11 network as well as with an ns3-simulation, whereby a very good agreement is achieved (a difference less than 2%).