The COVID-19 pandemic has impacted families’ lives around the world. The measures used to contain transmission have led to increased stress and put parents at increased risk for parental burnout (PB). The aim of the current study was to examine the association between COVID-related parental stress and PB, and to test whether emotion regulation (ER) moderated this association. We hypothesised that rumination, which is a generally maladaptive ER strategy, would act as a risk factor. In comparison, we hypothesised that reappraisal, which is a generally adaptive ER strategy, would act as a resilience factor. We assessed 8225 parents from 22 countries using an on-line survey, and focused on general stress and parenting stress. These stressors were associated with greater PB. Importantly, parental ER moderated these associations; rumination strengthened the link between stress-related variables and PB, whereas reappraisal weakened it. This study emphasises the negative effect COVID-19 has on parents and highlights key ER risk and resilience factors.