Loneliness is a significant threat to well-being and was exacerbated by the COVID-19 pandemic, especially for vulnerable groups such as mothers of young children. Although much needed, research on protective factors against maternal loneliness is lacking. The present study aimed to address this gap by investigating whether reflection, understood as curiosity-driven self-focused attention, could moderate the relationship between loneliness and eudaimonic well-being (EWB) during the pandemic. The hypotheses predicted that loneliness in the romantic, family, and social domains would be negatively associated with EWB, and that these relationships would weaken with an increase in reflection. In a cross-sectional study of 559 Polish women (aged 20–46, M = 30.72, SD = 4.11) with one child under 6 years, participants completed measures of loneliness, EWB, and reflection, with rumination as a covariate. We used the latent variable interaction approach to test main and interaction effects. As hypothesized, loneliness domains negatively correlated with EWB, moderated by reflection. Higher reflection weakened links between social and family loneliness and EWB. Considering that the cognitive characteristics of reflection can be effectively developed through training, these findings can inspire psychological interventions dedicated to coping with the loneliness experienced by mothers of young children.