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.