Within the recent upsurge in empirical research around the effects of mindfulness, its negative association with burnout has emerged to be one of the most robust findings. However, the mechanisms of this association remain a subject for discussion. This study examined the mediating role of seven habitual emotion regulation strategies in the impact of dispositional mindfulness during the onset of the COVID-19 pandemic. To this end, primary data were collected from 112 German professionals of diverse occupations via an online survey and analysed using mediation analysis. Results showed that dispositional mindfulness was inversely related to burnout symptoms. Reduced rumination and increased acceptance partially explained this relation, whereas the other tested strategies did not add incremental variance explanation. These results support previous findings promoting mindfulness during stressful periods and highlight the habitual application of acceptance and rumination as core mediating mechanisms. However, given their substantial correlation, further research should examine whether these are two separate mechanisms of action.