The Just Beginning (JB) intervention aims to improve the quality of interactions between fathers with low incomes and their young children. This intervention was implemented at a fatherhood program site in Philadelphia, Pennsylvania. Fathers participated in up to five sessions of the JB program, which included unstructured play sessions with their young children. In this paper, we use growth curve models to estimate patterns of change across the five sessions in the quality of the father-child interactions, drawing on 152 video observations from 53 father-child dyads. We find that fathers’ positive regard toward their children increased across JB sessions, but do not find statistically significant changes in other indicators of fathers’ positive parenting behaviors or in fathers’ negative parenting behaviors. Estimating results for nonresident and resident fathers, we find that improvements in positive parenting behaviors appeared to be larger and more widespread for nonresident fathers than they were for fathers who lived with their focal children.