Parental warmth and child emotion regulation have each been implicated in the development of child pro-social behaviours; however, their interactive benefits remain unclear. In this multi-method, multi-cohort longitudinal study, we examined the effect of parental warmth on child pro-social behaviours at different levels of child emotion regulation. We collected data from 6- and 10-year-olds in Canada (N
T1 = 233; M
age = 8.41; SD = 2.08) and their parents. Parental warmth, child emotion regulation, and child pro-social behaviours were assessed via parent report. Children’s baseline respiratory sinus arrhythmia (RSA; an indicator of cardiac regulatory capacity) was assessed as a correlate of emotion regulation. Child pro-social behaviours were assessed concurrently and 1 year later. Results showed that higher parental warmth was related to higher concurrent prosocial behaviours and greater increases in prosocial behaviours over 1 year. These effects were strengthened for children with higher emotion regulation whether measured by parent report or RSA. We discuss implications for understanding pro-social development in middle childhood from a strengths-based perspective.