Much is known about how having a teenage mother influences children's outcomes, but the relationship between teenage fatherhood and children's health and development is less well documented. Using the Early Childhood Longitudinal Study-Birth Cohort, the authors investigated how teenage fathers matter for children. They expected teenage fathers' influence on children to differ from adult fathers' in three domains: the household context, the father-mother relationship, and the father-child relationship. Teenage fathers were less often married and more often cohabiting or nonresident, and their children experienced a variety of social disadvantages in their household contexts. The quality of the father-child relationship did not often differ between adolescent and adult fathers. Fathers' marital status and children's household contexts each fully explained the negative relationship between having a teen father and children's cognitive and behavior scores at age 2. These findings suggest that policy interventions could possibly reduce these children's developmental gaps in the critical preschool years. (Contains 2 tables and 4 notes.)