This study examines associations between maternal and paternal sensitive parenting and child cognitive development across the first 3years of life using longitudinal data from 630 families with co-residing biological mothers and fathers. Sensitive parenting was measured by observational coding of parent–child interactions and child cognitive development was assessed with the Bayley Scales of Infant Development and the Wechsler Preschool and Primary Scales of Intelligence. There were multiple direct and indirect associations between parenting and cognitive development across mothers and fathers, suggesting primary effects, carry-forward effects, spillover effects across parents, and transactional effects across parents and children. Associations between parenting and cognitive development were statistically consistent across mothers and fathers, and the cumulative effects of early parenting on later cognitive development were comparable to the effects of later parenting on later cognitive development. As interpreted through a family systems framework, findings suggest additive and interdependent effects across parents and children. •Complex sampling, longitudinal methods and analyses tested developmental hypotheses.•Mother and father sensitive parenting comparably predict early cognitive development.•There were direct, indirect, and transactional effects from both parents to child.•Findings support inclusion for mothers and fathers in interventions on this topic.