This study examined mothers’ and fathers’ beliefs about responding to infant night wakings across the first year of life, changes in those beliefs, and how individual maternal and paternal beliefs and interparental discrepancy in beliefs about responding to infant night wakings related to parents’ perceptions of coparenting quality. Participants were 167 mothers and 155 fathers who reported on their own beliefs about responding to infant night wakings and perceptions of coparenting quality when infants were 1, 3, 6, 9, and 12 months old. As predicted, mothers endorsed stronger beliefs about responding more immediately to infant night wakings than fathers, but for both parents these beliefs declined over the first year. Troubled beliefs about responding to infant night wakings predicted worse coparenting quality. In addition, the discrepancy between mothers’ and fathers’ beliefs predicted coparenting quality such that a larger discrepancy in parents’ beliefs about responding to infant night wakings significantly predicted poorer perceptions of coparenting, particularly in the early months, but only when mothers endorsed stronger beliefs than fathers. Results emphasize the importance of communication and concordance in nighttime parenting practices for aspects of parents’ coparenting relationship. Future research should consider the importance of examining domain-specific parenting practices and cognitions as well as interparental discrepancies when assessing coparenting quality.