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.