This paper uses data from the Fragile Families and Child Wellbeing Study (N = 2,098) to examine differences in the parenting practices of four types of resident fathers, defined by their biological relationship to a focal child and their marital status with regard to the focal child's mother. Regression results suggest that biological fathers and social fathers (i.e., stepfathers or mothers' cohabiting partners) differ significantly, and in some unexpected ways, on most measures of parenting. A considerable portion of these differences, however, can be explained by variation in the background characteristics of the individuals and families in each group. Additionally, difference-in-difference analyses reveal a stronger link between marriage and higher quality parenting practices among social fathers than among biological fathers.