IntroductionNational breastfeeding rates have improved in recent years, however, disparities exist by socioeconomic and psychosocial factors. Suboptimal breastfeeding overburdens the society by increasing healthcare costs. Existing breastfeeding supports including education and peer support have not been sufficient in sustaining breastfeeding rates especially among low-income women. The preliminary outcomes of contingent incentives for breastfeeding in addition to existing support show promising effects in sustaining breastfeeding among mothers in the Special Supplemental Nutrition Programme for women, infants and children (WIC).Methods and analysisThis trial uses a parallel randomised controlled trial. This trial is conducted at two sites in separate states in the USA. Mothers who were enrolled in WIC and initiated breastfeeding are eligible. Participants (n=168) are randomised into one of the two study groups: (1) standard care control (SC) group consisting of WIC breastfeeding services plus home-based individual support or (2) SC plus breastfeeding incentives (SC +BFI) contingent on demonstrating successful breastfeeding. All participants receive standard breastfeeding services from WIC, home-based individual support and assessments. Participants in SC receive financial compensation based on the number of completed monthly home visits, paid in a lump sum at the end of the 6-month intervention period. Participants in SC +BFI receive an escalating magnitude of financial incentives contingent on observed breastfeeding, paid monthly during the intervention period, as well as bonus incentives for selecting full breastfeeding food packages at WIC. The primary hypothesis is that monthly incentives contingent on breastfeeding in SC +BFI will significantly increase rates of any breastfeeding compared with SC. The primary outcome is the rate of any breastfeeding over 12 months. Randomisation is completed in an automated electronic system. Staff conducting home visits for support and assessments are blinded to study groups.Ethics and disseminationThe Advarra Institutional Review Board has approved the study protocol (Pro00033168). Findings will be disseminated to our participants, scientific communities, public health officials and any other interested community members.Trial registration numberNCT03964454