The present study modeled the associations between adolescent mothers’ and young fathers’ perceptions of partner conflict, parenting alliance, fathers’ prenatal involvement, and father engagement with infants using a sample of 127 adolescent mothers and their partners. This study hypothesized that (a) higher quality parenting alliances would be associated with increased father engagement with infants, (b) prenatal partner conflict would have a negative spillover effect on the parenting alliance and father engagement during infancy, and (c) fathers’ prenatal involvement would be positively associated with parenting alliance and engagement during infancy. The results showed that mothers’ perceptions of parenting alliance during infancy were robust correlates of father engagement, mothers’ perceptions of prenatal partner conflict had a negative spillover effect on parenting alliance and father engagement with the infant as perceived by mothers, and fathers’ and mothers’ perceptions of fathers’ prenatal involvement were directly linked to engagement with infants.