ObjectiveTo examine whether adverse childhood experiences (ACEs) confer risk for socio-emotional problems in children born very preterm (VPT) Study designAs part of a longitudinal study, 96 infants born VPT at 23-30 weeks of gestation were recruited from a level III neonatal intensive care unit and underwent follow-up at ages 2 and 5 years. Eighty-three full-term (FT, 37-41 weeks gestation) children were recruited from an adjoining obstetric service and the local community. ACEs were assessed with the Child Life Events Scale at age 2 and Preschool Age Psychiatric Assessment at age 5. At age 5, internalizing, externalizing, and Attention-Deficit/Hyperactivity Disorder (ADHD) symptoms were assessed with the Child Behavior Checklist and Conner’s Rating Scale-Revised, respectively. Covariates including socioeconomic disadvantage, maternal distress, and parent ADHD symptoms were assessed at the 2- and/or 5-year follow-up. Mediation and moderation analysis, accounting for family clustering, examined associations between birth group, ACEs, and socio-emotional outcomes. ResultsAfter covariate adjustment, children born VPT experienced more ACEs (p<0.001), particularly medical ACEs (p<0.01), and had worse ADHD and internalizing outcomes (p<.05) than FT children. ACEs mediated the association between birth group and ADHD outcomes (95% CIs: 0.11 – 4.08). There was no evidence of mediation for internalizing outcomes. Higher parent ADHD symptoms (p<.001) and maternal distress (p<.05) were associated with poorer internalizing outcomes. ConclusionsScreening for childhood ACEs should be embedded in the follow-up care of children born VPT and their families. Strategies to screen for and address parent psychosocial functioning may be important to support children’s socio-emotional development.