The relationships between ethnicity, socio-economic status (SES) and health-related quality of life (HRQoL) have not been well characterised in most Asian populations. We therefore studied the influence of ethnicity and SES on HRQoL in a multi-ethnic urban Asian population, adjusting for the influence of other known determinants of HRQoL. In a disproportionately stratified, cross-sectional, population-based survey, Chinese, Malay and Indian subjects in Singapore completed the Short Form 36 Health Survey (SF-36) HRQoL measure and were assessed to determine demographic, socio-economic, psychosocial and other characteristics. Multiple linear regression models were used to study the influence of ethnicity and SES on SF-36 scores while adjusting for the influence of other determinants of HRQoL. The survey participation rate was 92.8%. Ethnic differences in HRQoL were present for all 8 SF-36 scales (p<0.001 for all scales except General Health) among the 4122 Chinese, Malays and Indians surveyed. These ethnic groups also differed in several known determinants of HRQoL (e.g., Chinese had more years of education and Indians had more chronic medical conditions). After adjusting for the influence of these factors, ethnicity and SES independently influenced HRQoL, with mean differences in SF-36 scores due to ethnicity ranging from 1.4 to 13.1 points. Educational level and housing type (markers of SES) were also associated with SF-36 scores (0.5-0.6 point increase per year of education and 3.5-4.0 point increase with better housing type, respectively). Better HRQoL was also associated with better family support, and poorer HRQoL with acute and chronic medical conditions and sick days. The study concludes that ethnicity and SES are associated with clinically important differences in HRQoL in a multi-ethnic, urban Asian population.