Evidence of gender differences in parental burnout has been replicated in several studies and in several cultures, showing a higher level of parental burnout in mothers but a greater sensitivity of fathers to this serious condition. However, the reasons for these differences have never been tested empirically. In this study, we tested whether mothers’ higher level of burnout is related to their greater investment in parenting activities. We also tested the greater sensitivity of fathers to a stress factor that is highly associated with parental burnout, emotion regulation. 1,322 Brazilian parents (41.3% fathers) participated in the study during the pandemic, which was regarded as a context in which parental stress naturally increased. The results confirmed mothers’ higher mean level of parental burnout. Contrary to our expectations, the results also revealed that mothers still experienced higher parental burnout than fathers even when we strictly controlled for the level of involvement in parenting. They also showed that compared to fathers, mothers were more susceptible to emotion dysregulation and to a stressful situation affecting parenting (i.e. the pandemic). Avenues for future studies are twofold. First, they should investigate alternative explanations for gender differences in parental burnout. Second, to the extent that gender moderates the impact of risk factors on parental burnout, future studies should identify specific risk factors for mothers on the one hand and for fathers on the other.