Although existing research recognized the associations between early maladaptive schemas (EMSs) of parents and their adult children, the mechanisms that underpin these associations were not fully understood. Therefore, the purpose of the current study was to explore the role of defence styles (DSs) on the associations between two EMS domains (Disconnection/Rejection and Impaired Autonomy) of parents and their adult children. Two hundred and fifteen families (i.e., mother, father, and their adult children) participated in the study. Both parents and their adult children were asked to complete Young Schema Questionnaire-Short Form (YSQ-SF) and Defence Style Questionnaire (DSQ) to assess their EMS domains and DSs. According to the results of the current study, there were significant associations between Disconnection/Rejection and Impaired Autonomy EMS domains of parents and their adult children, and these associations were mediated by only immature DS of parents and their adult children in a serial mediation model. These results contributed to our understanding of the associations between EMS domains of parents and their adult children through immature DSs. Moreover, our findings highlighted the importance of synthesizing the concepts of different theories to enhance our understanding of mental representations in families.