["Family Process, Volume 65, Issue 3, September 2026. ", "\nABSTRACT\nMaternal depressive symptoms, especially given their severity and chronicity, can pose risks to children's peer competence. Yet, there is a potential for positive family expressions to buffer this effect. Guided by a developmental cascades framework, this study focused on a three‐way interaction among children's peer competence at school entry, positive family expressions, and maternal depressive symptoms in predicting children's peer skills over the elementary school years among U.S. families (N = 1364). Peer competence and positive peer interactions were measured through parental reports and school observations, respectively, in Grades 3 and 5. Positive family expressions were assessed by two caregivers in Grades 3, 4, and 5, and maternal depressive symptoms were self‐reported in Grades 1, 3, and 5. A path model revealed a three‐way interaction: children with higher peer competence in Grade 1 showed lower positive peer interactions in Grade 5, only under high levels of maternal depressive symptoms and high positive family expressions. In addition, maternal depressive symptoms predicted lower peer competence in Grade 5 under high positive family expressions. The findings underscore person–environment interactions in peer competence development and suggest a nuanced understanding of the role of positive emotion socialization in contexts of high maternal depressive symptoms. These findings emphasize the need for family‐based interventions addressing maternal depressive symptoms and children's social competence.\n"]