Despite compliance with national (RIVM) guidelines, nursing home Mariënburght (the Netherlands) was severely affected during the first COVID-19 wave: 68 (68%) of the residents were infected. This resulted in a large emotional impact on the (nursing) staff. This study aims to describe the experiences of (nursing) staff, as well as the results of serological tests on COVID-19 that have been administered to professionals. All professionals (n=281) were invited for group interviews to share their experiences concerning the COVID-19 outbreak and for a serological test for COVID-19. The 29 professionals participating in the group interviews mentioned negative and positive experiences about their fear and anxiety, the changed care for residents, the team spirit, the use of personal protective equipment and the testing policy. Out of 240 professionals who underwent the serological test and completed a questionnaire, 94 professionals (39%) had COVID-19 antibodies. In this group, 18 professionals (19%) indicated not having experienced any (physical) complaints related to COVID. Insight into the experiences of professionals resulted in essential learning points, in particular the importance of clear communication with and emotional support for staff. This study also reveals that many professionals of nursing home Mariënburght were affected by COVID-19. An important finding is the high percentage of asymptomatic employees (19% of 94 infected). Our results contributed to changed national testing policies and adapted recommendations in the use of personal protective equipment in nursing homes.