Parental emotion regulation is closely associated with the development of young children's behavioral problems. The present study aims to investigate the potential mediating role of family emotional expressiveness in the association between parental emotion dysregulation and externalizing problems among Chinese preschoolers and to further examine whether this mediation depends on parental endorsement of the cultural value of Chinese familism. A survey study was conducted to examine the moderated mediation model. A total of 161 parents of preschoolers (aged 3-5 years, M = 4.24, SD = 0.60 at T1) participated in all three waves of assessment. The results showed that parental emotion dysregulation indirectly predicted preschoolers' externalizing problems through family negative expressiveness for parents with low endorsement of familism, whereas the mediating effect was not significant for parents with high endorsement of familism. The results contribute to the literature on emotional parenting in the Chinese cultural context and underscore the role of familism values in the relationship between emotional parenting factors and children's behavioral problems. (PsycInfo Database Record (c) 2025 APA, all rights reserved).