Background Ethnic minority groups in western European countries tend to have higher levels of type 2 diabetes mellitus (DM) than the majority populations for reasons that are poorly understood. Investigating differences between countries could enable an investigation of the importance of national context in determining these inequalities. We determined whether the lower prevalence of DM in England vs the Netherlands is also observed in South-Asian-Indian and African-Caribbean populations. Additionally, we assessed the contribution of health behaviour, body sizes and socio-economic position to any observed differences between countries. Methods Secondary analyses of population-based standardised individual level data of 3386 participants. Differences in prevalence ratios (PR) of DM were estimated using regression models. Results Indian and African-Caribbean populations had higher prevalence rates of diabetes than Whites in both countries. In cross-country comparisons, similar to Whites, English-Indians had a lower prevalence of diabetes than Dutch-Indians; the difference in women remained after adjustments for other covariates (PR=0.35, 95% CI 0.22 to 0.55). English-African women also had a lower prevalence of diabetes than Dutch-Africans (PR=0.43, 95% CI 0.20 to 0.89). For African men the difference was small (p=0.249). Conclusion These findings suggest that the increasing prevalence of diabetes following migration may be modified by the context in which ethnic minority groups live.