ObjectivesThis study aimed to explore the association between positive mental health and mindful parenting among Portuguese new mothers by analyzing the mediating role of parenting stress. The moderating role of the perceived impact of COVID-19 on this association was also explored.MethodSample collection occurred between November 2020 and March 2021. Data from 142 women with a child aged up to 2 years old were collected online through self-report measures. Simple mediation and moderated mediation models were employed while controlling for maternal sociodemographic and health-related data.ResultsAfter controlling for the number of children and clinically significant symptoms of anxiety and depression, lower levels of maternal positive mental health were associated with lower levels of mindful parenting through higher levels of parenting stress. The association between positive mental health and parenting stress was more pronounced when mothers perceived the impact of COVID-19 as negative.ConclusionsOur results suggest the relevance of positive dimensions of maternal mental health during early parenting. These appear to contribute to parenting stress, especially under stressful perceived circumstances such as those related to the COVID-19 pandemic, and to maternal mindful parenting skills. It seems important to assess and intervene early in women’s positive mental health and parenting stress, even in the absence of psychopathology, so that new mothers are more likely to adopt adaptive parenting approaches, such as mindful parenting.PreregistrationThis study is not preregistered.