OBJECTIVES: With the spread of COVID-19, the Netherlands implemented a policy to keep citizens physically distanced. We hypothesize that consequent reduction in the frequency of social contacts, personal losses, and the experience of general threats in society reduced well-being. METHODS: Data were collected from 1,679 Dutch community-dwelling participants aged 65-102 years comprising a longitudinal online panel. Social and emotional loneliness and mental health were measured in May 2020, that is, 2 months after the implementation of the measures, and earlier in October and November 2019. RESULTS: In this pandemic, the loneliness of older people increased, but mental health remained roughly stable. The policy measures for physical distancing did not cause much social isolation but personal losses, worries about the pandemic, and a decline in trust in societal institutions were associated with increased mental health problems and especially emotional loneliness. DISCUSSION: The consequences of long-term social isolation and well-being must be closely monitored.