The COVID-19 pandemic substantially affected the lives of mothers. This study seeks to investigate the stress that mothers experienced during the COVID-19 pandemic and their self-efficacy as parents in managing the impact of the disease. The study gathered longitudinal data from 603 German mothers (M[subscript age] = 40.5 years) with children requiring daily care during local lockdowns. The data were collected at two measurement points before and two measurement points during the pandemic. Using bivariate dual change score models, this study investigated the bidirectional relationship between both constructs, perceived stress and parental self-efficacy, by considering mothers' socioeconomic background as well as COVID-19 related perceptions. The results reveal bidirectional paths between mothers' perceived stress and parental self-efficacy. Mothers who evaluated the current situation as stressful appeared to be at risk of perceiving themselves as less effective in their parenting over time, but especially during the pandemic. In addition, mothers' levels of education and their subjective poverty was predictive of a general change in their levels of stress and parental self-efficacy.