In addition to the fears associated with contracting COVID-19, the pandemic has forced families across the United States to quickly transition to new patterns of living. These transitions present new stressors, including health-related concerns, new demands placed on families by lockdowns and stay-at-home orders, and the possibility of losing a job or inability to pay bills. Such stressors have the potential to disrupt collaboration between coparents in addition to basic family functioning. Drawing upon a family systems perspective, the current study thus sought to examine links between COVID-19-related stressors and family cohesion through coparental functioning. A total of 1,003 parent/caregivers (97% from the United States; 82% Caucasian, 74% female; M = 40.9 years old, SD = 8.5; M[subscript income] = $83,631, SD[subscript income] = $36,320) of school-age children completed an initial online survey from the end of March to the end of April of 2020. Of the initial sample, a total of 685 parents/caregivers completed weekly diaries for a month. Based on multilevel modeling, results suggested that, at the between-family level, coparental conflict mediated the impact of the stress of parenting/work demands and financial stress on family cohesion. At the within-family level, weekly spikes in health-related stress were associated with corresponding spikes in coparental conflict, which, in turn, were associated with drops in family cohesion. Results from the current study suggest that beyond the fears associated with contracting the COVID-19 virus, other key stressors associated with the emerging pandemic played a role in increasing coparental conflict, ultimately exacerbating family functioning.