The present study examined developmental pathways beginning in pregnancy and extending into early childhood that contribute to child emotion regulation (ER). Leveraging data from a sample of 157 mixed-sex couples, who largely identified as White and non-Hispanic/Latino, and their typically developing children (50.3% female), we examined whether parental emotion-related socialization behaviors (ERSBs; i.e., general emotion talk, specific supportive and nonsupportive responses to children’s negative emotions) at preschool age (child age 3) mediated the link between parental trauma-related distress spanning pregnancy to toddler age (2-years postpartum) and child maladaptive ER at the transition to formal schooling (age 5). Chronic elevations in maternal trauma-related distress contributed directly and indirectly to child maladaptive ER at age 5, and maternal nonsupportive responses emerged as a potential pathway driving the intergenerational transmission of emotion dysregulation. In contrast, paternal trauma-related distress neither undermined ERSBs nor contributed to child maladaptive ER. Instead, chronic elevations in paternal trauma-related distress predicted more supportive responses to children’s negative emotions. Results highlight the utility of repeated screening for trauma-related distress and prevention and early intervention efforts targeting parental trauma-related distress and nonsupportive responses to children’s negative emotions. These strategies may help promote adaptive ER at school entry and reduce risk for later psychopathology.