The COVID-19 pandemic shapes the lives of people around the globe – at the same time, people themselves have the power to shape the pandemic. By employing protective health behaviour, the population can alleviate the severity of an outbreak. This may be of particular importance whenever health systems or populations are vulnerable to shocks, as is frequently the case in low- and middle-income settings. Therefore, understanding the underlying drivers of protective action against COVID-19 is urgently needed for policy responses. We investigate the individual-level determinants of disease knowledge and behaviour in the context of the COVID-19 pandemic in Aceh, Indonesia. We use data from a representative sample of 40–70-year-olds, mainly obtained from telephone interviews between March and May 2020. We employ linear probability models that account for a comprehensive set of factors that were previously found to influence knowledge and practice during pandemics. We find that both knowledge and uptake of protective health behaviour are relatively high. Knowledge is the largest explanatory driver of protective health behaviour, while socioeconomics and economic preferences are minor determinants. However, knowledge itself is strongly shaped by socioeconomic gradients. On this basis, we show that policies need to disseminate information in an equitable way.