Although the effects of non-state actor violence on public health outcomes are well known, the effects of public health crises like the COVID-19 pandemic on non-state actor violence are not. Lockdown measures, widely used to stop the spread of disease in crises, we argue, are likely to reduce non-state actor violence, especially in urban and non-base areas. These measures deplete actors’ resources, reduce the number of high-value civilian targets, and make it logistically more difficult to conduct attacks. Using the example of the Islamic State of Iraq and Syria (ISIS), and taking advantage of the exogenous nature of COVID-19 lockdowns, we find that curfews and travel bans significantly reduce violence, especially in populated and non-base areas. These effects are most likely due to short-term changes in ISIS’s targets and logistics rather than its resources. These findings provide important insights into the security aspects of public health crises and offer novel findings into the general effectiveness of two common counterinsurgency tools.