Using a sample of resident fathers in the Early Childhood Longitudinal Study-Birth Cohort (9-month Father Study), this study examined how father involvement is associated with infant cognitive outcomes in two domains (babbling and exploring objects with a purpose). Results from a series of logistic regression models indicate that varied aspects of father involvement (cognitively stimulating activities, physical care, paternal warmth, and caregiving activities) are associated with a lower likelihood of infant cognitive delay. Two-way interaction models further indicate that father involvement is related to greater reductions in infant cognitive delay for male infants than for female infants and for infants with disabilities than for infants without. These findings point to the importance of considering fathers' roles in early infant outcomes. Early positive father-child interactions reduce cognitive delay. (Contains 3 tables.)