This study examined whether coparenting support and social support had a stronger effect on father engagement with 3-year-olds among adolescent fathers compared with adult fathers. Using data from the Fragile Families and Child Wellbeing Study (N = 1,540), we found that coparenting support and paternal social support had a significantly stronger positive effect on adolescent fathers than adult fathers. The associations among coparenting, social support, and adolescent father engagement did not depend on whether the father and mother were romantically involved with each other. The results support the idea that programs for adolescent parents should focus on coparenting and social support as a way to help fathers to stay involved with their children.