The study of adolescent childbearing is a major public policy concern in the United States, and father involvement is particularly important. The current study examined 94 African American and Latino adolescent mothers and their children's fathers (47 co-parents) to determine whether co-parenting was a better predictor of father involvement than was relationship quality and whether postnatal co-parenting mediated the relationship between prenatal relationship quality and postnatal father involvement. Results were mixed; a full structural equation modeling (SEM) model primarily supported previous literature, suggesting that, according to mothers, postnatal co-parenting was the strongest predictor of father involvement. However, when postnatal relationship quality was added to a regression analysis, co-parenting did not predict father involvement. Further, a mediation analysis did not support a mediating effect of co-parenting on the association between relationship quality and father involvement. The results of this study suggest that relationship quality may be of equal or greater importance than the co-parenting relationship as a potential point of intervention for improving father involvement in adolescent African American and Latino parents.