The effect of the COVID-19 pandemic on life satisfaction has been a topic of worldwide research, mostly indicating a drop in individual’s life satisfaction with some differences between subgroups. However, literature on related mechanisms is scarce. This study examines whether the sense of social belonging is a mechanism that explains pandemic-related changes in life satisfaction across different age groups. Using a rich longitudinal data set of the adult cohort of the German National Educational Panel Study and employing fixed effects panel regression models, we show that the COVID-19 pandemic is, on average, negatively associated with individual life satisfaction and social belonging. Yet, mediation and sensitivity analysis questions the general importance of social belonging as a relevant mechanism irrespective of individuals’ age. The results also suggest that the negative effects of the pandemic on social belonging were indeed significant for individuals with average or high pre-pandemic social belonging, while individuals with low pre-pandemic social belonging experienced an increase in their sense of social belonging. This leads to an expanded discussion of which groups of people are most affected by the impact of the COVID-19 pandemic and what other mechanisms can be hypothesized to explain this negative impact on people's life satisfaction.