Research on fathers in Early Head Start (EHS) has provided an opportunity to study fathers from low-income families. We examined father-toddler social toy play in relation to EHS enrollment, fathers' psychosocial well-being, and children's developmental outcomes in a sample of 74 father-toddler dyads. Overall, our results show that father-toddler social toy play was more complex among fathers in an EHS program than among those in a comparison group. Greater complexity in father-toddler social toy play predicted better cognitive and social developmental outcomes for young children, especially in the program group, but it was limited by fathers' psychosocial well-being in the comparison group and by time availability in the program group. Nevertheless, the impact of EHS on father-toddler play suggests that an early intervention that targets father involvement can influence positive father-toddler interactions in ways that enhance early development.