<p>Work–family conflict is a prevalent issue among parents of preschool children, and prolonged exposure to such conflict can significantly impact the social adjustment of preschool children. In this study, we conducted a cross-sectional design to investigate the relationship between parental work–family conflict and preschool children’s social adjustment, as well as the mediating role of authoritarian parenting behavior and the moderating role of coparenting. A total of 537 preschool children (<i>M</i>_age = 62.05 ± 12.54 months) and their parents (<i>M</i>_<i>a</i>ge = 38.15 ± 4.63 years) participated in the study. Parents completed the Work–Family Conflict Questionnaire, Coparenting Questionnaire, Parenting Styles and Dimensions Questionnaire,and Social Competence and Behavior Evaluation.The findings revealed several key insights: (1) Parental work-family conflict was significantly negatively correlated with preschool children’s social adjustment; (2) Authoritarian parenting style mediated the relationship between work-family conflict and preschool children’s social adjustment; (3) Coparenting moderated the first half path of the mediation model, indicating that the impact of parental work–family conflict on preschool children’s social adjustment through authoritarian parenting behaviors was more pronounced under low level coparenting compared with high levels of coparenting. The results provide empirical evidence for the importance of mitigating parental work–family conflict and enhancing coparenting practices to improve preschool children’s social adjustment. The study underscores the need for interventions that address both work–family balance and parenting behaviors to foster better social outcomes for young children.</p>