Due to the inherent demands of their profession, doctors and nurses are at great risk of suffering from burnout caused by job stress. This study examined the prevalence of burnout among doctors and nurses in Mongolia and identified the factors influencing their burnout. A self-administered questionnaire of 180 doctors (45.9%) and 212 nurses (54.1%) resulted in a response rate of 87%. Burnout was measured by the Copenhagen Burnout Inventory (CBI) in three scales: personal burnout, work-related burnout, and client-related burnout. Job stress was measured by the effort-reward imbalance (ERI) model. Compared with the prior studies of hospital staffs in other countries, doctors and nurses in Mongolia had relatively higher burnout rates, with personal, work-related and client-related average scores of 45.39, 44.45, and 32.46, respectively. Multiple regression analysis revealed that ERI significantly influenced all dimensions of burnout but over-commitment significantly influenced only personal and work-related burnout. Both ERI and over-commitment were different among professions.