The Longitudinal Aging Study Amsterdam (LASA) is an ongoing cohort study among older adults in the Netherlands. Respondents are usually interviewed approximately every 3 years. Because of the exceptional situation of the COVID-19 pandemic, it was decided to add an extra assessment in between, consisting of a postal/digital questionnaire with measures assessing the impact of the COVID-19 situation, as well as a selection of measures from regular LASA measurement cycles covering the physical, social and mental domains. In total, 1128 LASA respondents aged 62–102 years provided data, just after the first wave of the pandemic in 2020. This paper describes the methods and design of the LASA COVID-19 questionnaire, as well as the basic characteristics of the sample, including an overview of impactful situations experienced by older adults during the first months of the pandemic. The data of the questionnaire may be used to study the impact of the COVID-19 pandemic on multiple domains of functioning in older adults.