We describe the development and validation of the Daily Coparenting Scale (D-Cop), a measure of parents’ perceptions of daily coparenting quality, to address the absence of such a daily measure in the field. A daily measure of coparenting can help us to better identify specific mechanisms of short-term change in family processes as well as examine within-person variability and processes as they are lived by participants in their everyday lives. Mothers and fathers, from 174 families with at least one child age 5 or younger, completed a 14-day diary study. Utilizing multilevel factor analysis, we identified two daily coparenting factors at both the between- and within-person level: positive and negative daily coparenting. The reliabilities of the overall D-Cop and individual positive and negative subscales were good, and we found that parents’ reports of coparenting quality fluctuated on a daily basis. Also, we established the initial validity of the D-Cop, as scores related as expected to (a) an existing and already validated measure of coparenting and to (b) couple relationship quality, depressive symptoms, and child behavior problems. Further, fluctuations in daily couple relationship feelings related to fluctuations in daily coparenting quality. The D-Cop and its subscales functioned almost identically when only utilizing 7 days of data instead of 14 days. We call for future work to study day-by-day fluctuations and dynamics of coparenting to better illuminate family processes that lead to child and family outcomes in order to improve the efficacy of family interventions.