We examined differences in health indicators and associated factors across countries according to the proportion of the population who are Muslim. Of 190 UN countries, 48 were classified as Muslim-majority countries (MMC) and 142 as non-MMC. Data on 41 potential determinants of health were obtained from 10 different data sources, and 4 primary outcome measures (male and female life expectancy, maternal mortality ratio and infant mortality rate) were analysed. Annual per capita expenditure on health in MMC was one-fifth that of non-MMC. Maternal mortality and infant mortality rates were twice as high in MMC as non-MMC. Adult literacy rate was significantly higher for non-MMC. Four significant predictors explained 52%-72% of the differences in health outcomes between the 2 groups: gross national income, literacy rate, access to clean water and level of corruption.