Nepal's female community health volunteers (FCHVs) each lead a monthly health mothers’ group (HMG) to share health-related information and engage communities in the health system. In this study, we explored HMG functionality and variation across Nepal, including barriers and facilitators to attending HMG meetings. Cross-sectional survey data from 16 districts (n = 192 FCHVs and 1850 mothers with children <2y) were used. Qualitative data were obtained from 3 of 16 survey districts (n = 30 observations, n = 30 in-depth interviews with mothers, and n = 16 focus groups with mothers, family members, FCHVs, health workers, and SII staff). Household head sex, maternal age, maternal education, maternal self-efficacy, and engagement with an FCHV were associated with whether mothers were active participants in meetings. Qualitative findings highlighted systems-level barriers, including lack of FCHV skills, demotivation, and heavy workload. Mothers noted time as the major constraint and family support, the HMGs' savings component, and active FCHVs as facilitators to participation. Findings suggest that both supply- and demand-side solutions are needed to improve HMG performance and uptake in Nepal.