Emerging literature suggests fathers may contribute uniquely to child development and emotional health through play. In the present study, a multiple mediational model was analyzed using data from 476 families that participated in the NICHD Study of Early Child Care and Youth Development. After accounting for infant-mother attachment, infant temperament, and family income and stability, a significant indirect effect from father-child play quality to adolescent internalizing symptoms was found through father-reported child emotional dysregulation, B = -.05, 95% confidence interval; CI [-.14, -.01]. Specifically, in first grade, dyads where fathers were rated highly on sensitivity and stimulation during play, and children demonstrated high felt security and affective mutuality during play, had children with fewer father-reported emotional dysregulation problems in third grade, B = -.23, 95% CI [-.39, -.06]. Children with fewer emotional dysregulation problems had lower self-reported internalizing symptoms at age 15, B = .23, 95% CI [.01, .45]. Mothers' ratings of children's emotional dysregulation were not a significant mediator. Results are discussed regarding the importance of father-child play for children's adjustment as well as the usefulness of inclusion of fathers in child developmental research.