Objectives: Breast milk is considered to give protection against rotavirus infection since it contains anti-rotavirus maternal antibodies and other nonspecific inhibitors. Multilevel promotion of breastfeeding is a complex intervention that modifies behavioral determinants through multiple levels of health promotion. This intervention can prolong the duration and increase the prevalence of exclusive breastfeeding. This study aims to investigate the effect of multilevel promotion of breastfeeding on reducing the required budget for rotavirus vaccination in Indonesia. Methods: We developed an age-structured cohort model within a 5-year-time-horizon for the 2013 Indonesia birth cohort. We compared two situations: (i) baseline, reflecting the current situation for the population of under-5-years-old, and (ii) the current situation with an additional multilevel promotion of breastfeeding. We used Monte Carlo simulations to examine the economic acceptability and affordability of the rotavirus vaccination. Results: Vaccination coupled with multilevel promotion of breastfeeding could reduce rotavirus-diarrhea by 493,235 cases. At a vaccine price of US$ 5.0 per dose, multilevel promotion of breastfeeding could reduce the required budget for the implementation of three-dose rotavirus vaccination by US$ 50,000, compared to the current absence of specific promotion. Conclusions: Multilevel promotion of breastfeeding could potentially reduce the required budget for rotavirus vaccination. Mortality rate and vaccine price were the most influential parameters on the sensitivity analyses.