Abstract Background Data from European studies suggest that well-being declined during the first year of the COVID-19 pandemic. However, the pandemic's consequences on an overall nations’ well-being remains inadequately explored, especially over time. This study aims to map the long-term impact of the pandemic on the subjective well-being (SWB) of Belgian citizens. Methods Using a repeated cross-sectional study design, data were collected in representative samples of the Belgian population at 5 different time points during the period from February 2020 until December 2022. Life evaluation was measured with the Cantril ladder. Positive and negative affect were assessed with the short version of the Positive and Negative Affect Schedule. ANOVA were used to evaluate the evolution in SWB. Moderation analyses were performed to investigate the differential impact of the pandemic for different age categories. Results Our results show that the pandemic negatively impacted the SWB of the Belgian population. Life evaluation (F(4,7605)=18.12, p<.001) and positive affect (F(4,7605)=16.83, p<.001) significantly decreased during the second wave and after the fourth wave compared to before the pandemic with a decline of .52 and .37 points respectively for life evaluation and a decline of .18 and .42 points respectively for positive affect (both on a scale between 0 and 10). No statistically significant differences in negative affect were found (F(4,7605)=1.08, p = 0.363). Citizens over the age of 50 appeared to be more resilient than younger citizens as the negative impact of the pandemic was either smaller or delayed in this group for all SWB indicators. Conclusions The COVID-19 pandemic clearly impacted the SWB of the Belgian population, and particularly the well-being of younger individuals suffered. We urge policymakers to consider all aspects of health during pandemics and to attend in particular the mental health needs of younger members of their society. Key messages • The COVID-19 pandemic and its related ...