Uncertainty is a challenging aspect of caring for children with Duchenne/Becker muscular dystrophies (DBMD). Although uncertainty is often perceived as a state to be avoided, hope may influence caregivers' perceptions of uncertainty as opportunity. The goal of this cross-sectional quantitative study was to pilot a novel measure of state-based hope, and test relationships among uncertainty, hope, spirituality, and coping efficacy in mothers of children with DBMD. Mothers (n = 202) were recruited through DuchenneConnect, Parent Project Muscular Dystrophy, and Cincinnati's Children Hospital. A one-component solution for the novel Parent Hope Scale explained 44.3% of the variance, and the measure showed high internal consistency. Higher hope (P < 0.001), further disease progression (P = 0.042), and older mother's age (P = 0.001) were significantly associated with lower perceptions of uncertainty. Mothers reporting less hope (P < 0.001), higher perceptions of uncertainty (P < 0.001), and less spirituality (P = 0.001) reported lower coping efficacy. As such, hope appears to be a key variable in shaping uncertainty appraisals and facilitating coping efficacy. While further research is needed, counseling aimed at bolstering hope, particularly among less-hopeful mothers, and interventions to reappraise uncertainty, may be helpful in promoting coping efficacy.