Intimate partner violence (IPV) between parents has been linked to negative parenting and child maladjustment, yet the mechanisms underlying this association are not fully understood. Based on a theory that violence among parents disrupts the coparental alliance--which has been linked to parenting quality and child adjustment--the authors examined the effect of prebirth violence on coparenting across the transition to parenthood. A community sample of 156 couples reported on IPV prior to the birth of their first child and on coparenting at child age 1 year. Both men and women's violence perpetration were related to coparenting quality. Couple relationship quality and parent mental health problems accounted for the links between prenatal IPV and coparenting. This study adds to an understanding of the associations between IPV and family functioning across the transition to parenthood, and has important implications for preventive intervention. (Contains 2 tables and 1 figure.)