The aim of this study was to examine health behaviours and happiness and associated factors in low, middle and high income countries. In a cross-sectional survey, 17 508 undergraduate university students (mean age 20.9, SD = 2. 8) from 25 universities in 24 countries across Asia, Africa and the Americas self-completed anonymous questionnaires. Results indicate that the overall happiness mean score among university students across 24 countries was 13.7 (range 4–20). Generally, the study found that university students from countries of the Caribbean, South America and sub-Saharan Africa had greater happiness scores than students from countries in North Africa and Asia. In multivariate linear regression analysis, better subjective socio-economic status, coming from an higher income country, higher social support, higher intrinsic religiosity, higher personal mastery, positive health behaviours (regular breakfast, adequate physical activity, habitual seatbelt use, regular dental check-ups, not having had an injury, not drinking and driving) and negative health behaviours (not having three or more servings of vegetables and eating red meat daily) were correlated with happiness. Improvement to the happiness of university students should consider regional differences in socio-economic environment.