A key component of outbreak control is monitoring public perceptions and public response. To determine public perceptions and public responses during the first 3 months of the coronavirus disease (COVID-19) outbreak in the Netherlands, we conducted 6 repeated surveys of ≈3,000 persons. Generalized estimating equations analyses revealed changes over time as well as differences between groups at low and high risk. Overall, respondents perceived the risks associated with COVID-19 to be considerable, were positive about the mitigation measures, trusted the information and the measures from authorities, and adopted protective measures. Substantial increases were observed in risk perceptions and self-reported protective behavior in the first weeks of the outbreak. Individual differences were based mainly on participants' age and health condition. We recommend that authorities constantly adjust their COVID-19 communication and mitigation strategies to fit public perceptions and public responses and that they tailor the information for different groups.