Although at arrival, US immigrants have a lower prevalence of overweight compared to native born individuals, prevalence increases with increased length of residence. It is unknown whether length of residence similarly affects diabetes. Data on adults aged 18-74 years from the National Health Interview Survey were pooled from 1997 to 2005 (n = 33,499). Diabetes prevalence by length of residence was estimated by multivariable logistic regression. Diabetes prevalence was higher with increased length of residence in the US, independent of age and body mass index (<5 years residence: 3.3%; 5-<10 year, 3.4%; 10-<15 year, 4.5%; 15+ year, 5.3%; P for trend <0.001). Length of residence had the largest effect on diabetes prevalence among immigrants who arrive at 25-44 years of age (prevalence: 1.4% for <5 year vs. 11.1% for 15+ year; odds ratio = 9.7 (95% CI: 5.2-18.1)). Despite differences in the associations between diabetes prevalence and length of residence by age at immigration, diabetes prevalence at 10-≤15 and 15± years was statistically similar in each age at immigration strata. Diabetes prevalence increased with length of residence, independent of age and obesity, and was modified by age at immigration. Diabetes prevalence reaches a plateau at 10+ years of residence and diabetes prevention efforts should, therefore, start soon after migration.