Detrimental impacts of early ecological adversity on children’s development are known, but our understanding of their mechanisms and factors contributing to multifinality of developmental trajectories triggered by adversity is incomplete. We examined longitudinal pathways from ecological adversity parents experienced when children were infants, measured as a cumulative index of fine-grained scores on several ecological risks, to children’s future self-regulation (SR) in 200 U.S. Midwestern community families (96 girls). Parents’ observed power-assertive styles were modeled as mediators, and their negative internal working models (IWMs) of the child, coded from interviews – as moderators. Both were assessed twice, at 16 months and at 3 years, to inform our understanding of their developmental timing. Children’s SR was reported by parents and observed at 4.5 years. Path analyses revealed moderated mediation in mother-child relationships: A path from higher early ecological adversity to elevated power assertion to children’s poorer SR was significant only for mothers with highly negative IWMs of the child. Maternal negative IWMs assessed early, at 16 months, moderated the link between ecological adversity and power assertion. Once elevated, maternal power assertion was stable through age 3 and not moderated by IWM at age 3. There were no significant effects in father-child relationships.