question: RATIONALE: An important public health strategy during the COVID-19 pandemic was the protection of people at risk of severe progressions of an infection; namely, older people and people with pre-existing conditions. OBJECTIVE: To improve public health communication, it is vital to understand, which sociodemographic and psychological factors drive older people’s acceptance of and compliance with public health measures. METHOD: This goal was pursued in this three-wave longitudinal online study with older adults, collected between March and June during the COVID-19 pandemic in 2020 (N = 327; first and second wave during the national lockdown; third wave: after the lifting of most lockdown measures). RESULTS: The results show that overall acceptance of and adherence to the public health measures were high among older adults and even more so for people with pre-existing conditions (e.g., cancer, type II diabetes). However, some infringements of the measures were observed, and the longitudinal analyses suggest that increases in social trust positively influenced acceptance of measures over time, while trivialising beliefs and health fears impacted older adults’ compliance with protective measures over time. CONCLUSIONS: This study offers insights into the behavioural responses of older adults to an ongoing threat and the associated uncertainty that is part of public communication about the pandemic and protective measures.