What are the consequences of the COVID-19 pandemic for people's political attitudes and behavior? We tested, specifically, whether the psychological burden of the COVID-19 pandemic relates to anti-systemic attitudes (dissatisfaction with the fundamental social and political order), peaceful political activism, and political violence. Nationally representative two-wave panel data were collected via online surveys of adults in the United States, Denmark, Italy, and Hungary (Ns = 6,131 and 4,568 in Waves 1 and 2 respectively). Overall, levels of anti-systemic attitudes were low and only a small share of interviewees reported behavioral intentions to participate and actual participation in political violence. However, pre-registered analyses indicated that perceived COVID-19 burden was associated with anti-systemic attitudes and intentions to engage in political violence. In the US, COVID-19 burden was also associated with self-reported engagement in violence surrounding the Black Lives Matter protests and counter-protests. We found less robust evidence that perceived COVID-19 burden was associated with peaceful activism.