ABSTRACT: BACKGROUND:Although individuals classified as nonresident aliens, including undocumented immigrants, are entitled to receive emergency dialysis in the United States regardless of their ability to pay, most states do not provide them with subsidized care for maintenance dialysis or kidney transplantation. We explored whether nonresident aliens have similar outcomes to US citizens after receiving kidney transplants covered by Medicaid, a joint federal and state health insurance program. STUDY DESIGN:Retrospective observational cohort study. SETTING & PARTICIPANTS:All adult Medicaid patients in the US Renal Data System who received their first kidney transplant from 1990 to 2011. PREDICTOR:Citizenship status, categorized as US citizen, nonresident alien, or permanent resident. OUTCOME:All-cause transplant loss. MEASUREMENTS:HRs and 95% CIs estimated by applying Cox proportional hazards frailty models with transplantation center as a random effect. RESULTS:Of 10,495 patients, 8,660 (82%) were US citizens, 1,489 (14%) were permanent residents, and 346 (3%) were nonresident aliens, whom we assumed were undocumented immigrants. Nonresident aliens were younger, healthier, receiving dialysis longer, and more likely to have had a living donor. 71% underwent transplantation in California, and 61% underwent transplantation after 2005. Nonresident aliens had a lower unadjusted risk for transplant loss compared with US citizens (HR, 0.48; 95% CI, 0.35-0.65). Results were attenuated but still significant when adjusted for demographics, comorbid conditions, dialysis, and transplant-related factors (HR, 0.67; 95% CI, 0.46-0.94). LIMITATIONS:Citizenship status was self-reported, possible residual confounding. CONCLUSIONS:Our study suggests that the select group of insured nonresident aliens who undergo transplantation with Medicaid do just as well as US citizens with Medicaid. Policymakers should consider expanding coverage for kidney transplantation in nonresident aliens, including undocumented immigrants, given the associated high-quality outcomes in these patients.