Since the start of the SARS-CoV-2 pandemic, levels of loneliness have increased among the general population and especially among sexual minorities, such as gay men and other men who have sex with men, who already experienced more problems with social isolation before the pandemic. We analyzed how the disruption of the social network and social support structures by containment measures impact loneliness among gay and other men having sex with men. Our sample consisted of gay and other men having sex with men who had in person communication with family as well as heterosexual friends and homosexual friends before the lockdown (N = 461). Multivariate regression analyses were performed with social provisions (social interaction and reliable alliance) and loneliness as dependent variables. A change from in-person communication with gay peers before the pandemic to remote-only or no communication with gay peers during the pandemic, mediated by change in social integration, was related to an increased feeling of loneliness during the pandemic compared with before the pandemic. There were some unexpected findings, which should be interpreted in the specific social context of the SARS-CoV-2 pandemic. On average, social integration and reliable alliance among MSM increased during the lockdown, even though in-person communication decreased and loneliness increased. Our results show it is critical to maintain a view of social support and social loneliness as lodged within larger social and cultural contexts that ultimately shape the mechanisms behind them.