This study uses data on 2,494 new fathers from the Fragile Families Study to analyze why and how the arrival of a new child may influence fathers' well-being and social participation. Our regression results indicate that changes in commitments to fathering are positively associated with changes in well-being, religious participation, and hours in paid labor. The one exception is that increases in fathers' engagement activities with their new child are negatively associated with changes in their hours in paid labor. The findings suggest that increases in commitments to fathering after the arrival of a new child are generally beneficial for fathers. In addition, greater commitments to fathering seem likely to benefit mothers, children, and society at large.