Until a vaccine becomes available, a frequently adopted strategy to contain the COVID-19 pandemic involves three non-pharmaceutical interventions that crucially depend on high adherence in society: maintaining physical distance from others, minimizing social contacts, and wearing face masks. These measures require substantial changes in established practices of social interaction, raising the question of which factors motivate individuals to comply with these preventive behaviours. Using Austrian panel survey data from April to October 2020 we show that perceived health risks, social norms, and trust in political institutions stimulate people to engage in preventive behaviour. Moderation analyses show that the effectiveness of social norms and trust in institutions in facilitating preventive behaviour increases when people’s perceptions of health risks decrease. This result suggests that trust in institutions and strong social norms play a crucial role in achieving high rates of preventive behaviour when perceived levels of health risks are low.