Maternal depression negatively affects young children’s emotional development, with varying impacts based on child gender and family structure, according to a study conducted in China. The research involved 726 mothers and utilized established scales to assess maternal depression, parenting styles, and children’s emotional competence. Findings revealed that maternal depression directly influenced emotional competence in girls and non-only children, while negative parenting styles mediated these effects across all groups. Specifically, the impact was significant for girls (b = -0.26) and non-only children (b = -0.41), but not for boys or only children. The study emphasizes the urgent need for targeted interventions to address maternal mental health, suggesting that community support and psychological counseling can help reduce negative parenting behaviors. Additionally, it advocates for parent education programs to promote effective parenting techniques, particularly for vulnerable groups such as boys and only children. The research highlights the importance of understanding family dynamics amid China’s shifting family policies, including the “Universal Two-Child” and “Three-Child” initiatives.