Amid increased acts of violence against telecommunication engineers and property, this pre-registered study (N = 601 Britons) investigated the association between beliefs in 5G COVID-19 conspiracy theories and the justification and willingness to use violence. Findings revealed that belief in 5G COVID-19 conspiracy theories was positively correlated with state anger, which in turn, was associated with a greater justification of real-life and hypothetical violence in response to an alleged link between 5G mobile technology and COVID-19, alongside a greater intent to engage in similar behaviours in the future. Moreover, these associations were strongest for those highest in paranoia. Furthermore, we show that these patterns are not specific to 5G conspiratorial beliefs: General conspiracy mentality was positively associated with justification and willingness for general violence, an effect mediated by heightened state anger, especially for those most paranoid in the case of justification of violence. Such research provides novel evidence on why and when conspiracy beliefs may justify the use of violence. During the COVID-19 pandemic, telecommunication masts across Europe, North America, and Australasia have been damaged or destroyed in arson attacks, while engineers have been subjected to verbal and physical abuse (Ankel, 2020; Cerulus, 2020; Pasley, 2020). Such violence not only seems unwarranted, attacking essential workers along with vital infrastructure, particularly during a global pandemic, is extremely irresponsible and dangerous (e.g., Cowburn, 2020). Why, then, have some individuals resorted to these senseless attacks? According to police officials and media commentators, the perpetrators are likely to be motivated by the erroneous conspiratorial belief that electromagnetic waves transmitted by 5G technology have somehow caused COVID-19 and so respond with violent actions to stop, what they see, as the origin of COVID-19 (e.g., Waterson & Hern, 2020). By empirically testing this assumption, the current research provides a timely and important investigation into the associations between conspiracy beliefs and violence to explore why and when conspiracy beliefs may justifyand igniteviolence. Conspiracy theories explain the ultimate causes of significant events as the secret actions of malevolent groups, who cover-up information to suit their interests (e.g., Douglas, et al., 2017). These beliefs tend to emerge in times of crisis in society (van This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.