BACKGROUND: Data on disparities in mortality within low and middle income countries are limited, with little published data from the Caribbean or Central America. Our aim was to investigate disparities in overall and cause specific premature adult mortality in the multi-ethnic middle income country of Belize. METHODS: Mortality data from Belize 2008-2010 classified using the International Classification of Diseases 10 and the 2010 census stratified by age and ethnicity were used to calculate age, sex, and ethnic specific mortality rates for those 15-59 years, and life table analysis was used to estimate the probability of death between the ages of 15 and 59 (45q15). RESULTS: The probability of death among those aged 15 to 59 years was 18.1% (women 13.5%, men 22.7%). Creole and Garifuna ethnic groups have three times the 45q15 probability of death compared to Mayan and Mestizo groups (Creole 31.2%, Garifuna 31.1%, Mayan 10.2%, Mestizo 12.0%). This pattern of ethnic disparity existed in both sexes but was greater in men. The probability of death from injuries was 14.8% among Creole men, more than twice the rate of other ethnicities and peaks among young Creole men. These deaths are dominated by homicides and unspecified deaths involving firearms. CONCLUSIONS: Marked disparities in mortality between ethnic groups exist in this Central American/Caribbean country, from rates that are typical of high-income countries to those of low-income countries. The pattern of these extreme differences likely suggests that they reflect underlying social determinants rooted in the country’s colonial past.