INTRODUCTION: Rotavirus disease in Mongolia is estimated to cause more than 50 deaths yearly and many more cases and hospitalizations. Mongolia must self-finance new vaccines and does not automatically access Gavi prices for vaccines. Given the country's limited resources for health, it is critical to assess potential new vaccine programs. This evaluation estimates the impact, cost-effectiveness, and budget implications associated with a nationwide rotavirus vaccine introduction targeting infants as part of the national immunization program in Mongolia, in order to inform decision-making around introduction. METHODS: The analysis examines the use of the two-dose vaccine ROTARIX®, and three-dose vaccines ROTAVAC® and RotaTeq® compared to no vaccination from the government and the societal perspective. We use a modelling approach informed by local data and published literature to analyze the impact and cost-effectiveness of rotavirus vaccination over a ten-year time period starting in 2019, using a 3% discount rate. Our main outcome measure is the incremental cost-effectiveness ratio (ICER) expressed as US dollar per DALY averted. We assessed uncertainty around a series of parameters through univariate sensitivity analysis. RESULTS: Rotavirus vaccination in Mongolia could avert more than 95,000 rotavirus cases and 271 deaths, over 10 years. Averted visits and hospitalizations represent US$2.4 million in health care costs saved by the government. The vaccination program cost ranges from $6 to $11 million depending on vaccine choice. From the governmental perspective, ICER ranged from $412 to $1050 and from $77 to $715 when considering the societal perspective. Sensitivity analysis highlights vaccine price as the main driver of uncertainty. CONCLUSION: Introduction of rotavirus vaccination is likely to be highly cost-effective in Mongolia, with ICERs estimated at only a fraction of Mongolia's per capita GDP. From an economic standpoint, ROTAVAC® is the least costly and most cost-effective product choice.