Aim This study aimed to investigate the potential protective role of eudaimonic well-being in mitigating the adverse effects of depressive symptoms. Background The dual continua model conceptualizes mental well-being and mental illness as related yet independent dimensions. According to this framework, well-being can serve as an active defense against mental illness. Objective Building on the dual continua model, the study aimed to investigate the relationship between depressive symptoms and life satisfaction and the potential moderating role of eudaimonic well-being. Methods This hypothesis was tested using a national sample of 17,357 people from 8,162 households in South Korea. Bayesian multi-level modeling was used for data analysis. Results The results showed that eudaimonic well-being moderated the relationship between depressive symptoms and life satisfaction. Depressive symptoms were found to have a significant negative effect on life satisfaction in individuals with low and moderate eudaimonic well-being. However, in individuals with high eudaimonic well-being, depressive symptoms had no significant effect on life satisfaction. Conclusion These results suggest that eudaimonic well-being plays an important role in mitigating the effects of depressive symptoms on life satisfaction.