Lack of social interaction is associated with a heightened sense of loneliness and, in turn, poorer psychological well-being. Despite the prevalence of communicating with others virtually even when physically alone, whether the social interaction--loneliness--well-being relationship is different between face-to-face and virtual interactions and between younger and older adults is relatively understudied. This 21-day diary study examined this question among younger (n = 91; M[subscript age] = 22.87) and older (n = 107; M[subscript age] = 64.53) Hong Kong participants during the early stage of the COVID-19 pandemic (March-May 2020). We found significant indirect effects of shorter face-to-face interaction time on poorer psychological well-being via a heightened sense of loneliness at the within-person level only among younger adults and at the between-person level only among older adults. Independent of loneliness, spending more time with others on virtual interactions was associated with better psychological well-being only among older adults. Taken together, while the mechanisms may be different across age groups, face-to-face interaction remains an effective way to reduce loneliness and enhance psychological well-being even at times when it is discouraged (e.g., pandemic). Although virtual interaction does not reduce loneliness, its positive impact on older adults' well-being sheds light on the utility of promoting technological acceptance in late adulthood.