We examined the extent to which fathers can be taught and encouraged to develop positive relationships with their children, especially in infancy, and the effects of this fathering intervention on infant development. A multifaceted relationally focused intervention was used to assist fathers in Vietnam to engage in responsive direct and indirect involvement with their infants and work together with the mother as part of a parenting team. Fathers and mothers from 13 communes in a rural and semiurban district were recruited to the intervention group. Intervention fathers received group and individual counseling before and after birth, an interactive print resource, community messages about fathering, and the opportunity to participate in a Fathers Club. Couples from 12 comparable communes in a noncontiguous district were recruited to the control group. Fathers and mothers completed questionnaires at the prebirth recruitment and at 1-, 4-, and 9-months postbirth. Intervention fathers demonstrated greater increase in knowledge and attitudes regarding father-infant relationships. Both fathers and mothers reported that fathers engaged in more affection, care-taking, and play in the early months of their infants' lives and fathers felt more attached to their infants right from birth. A developmental assessment at 9 months showed that intervention infants demonstrated higher levels of motor, language, and personal/social development. This study demonstrated that fathers can be taught to interact more sensitively, responsively, and effectively with their newborn infants. Their increased interaction and emotional attachment appears to lay the foundation for enhanced infant development.