Life course theory points to unique characteristics among older immigrants that may differentiate older age return migration from return at younger ages in terms of health. To investigate how the health of returnees may differ by age-at-return, this analysis compares disability between 3 groups of Mexican adults with a history of migration to the United States: those who return to Mexico before age 50, those who return at 50 and older, and those who remain in the United States at age 50 and older. Data from two nationally representative data sets, the U.S. Health and Retirement Study and the Mexican Health and Aging Study, are combined to create a data set representing Mexicans 50 and older with a history of migration to the United States. Adopting a life course perspective, activity of daily living (ADL) difficulty is compared by return status and age-at-return to account for differential selection into return by life stage. Mexican immigrants who remain in the United States past age 50 have a higher probability of at least 1 ADL compared to those who return to Mexico, regardless of life course timing of return. The immigrant disadvantage persists after adjusting for differences in demographic, childhood, and adult characteristics between groups. These findings are noteworthy because they stand in opposition to hypotheses based on life course and health-selective return migration theories and because they mean that Mexican immigrants remaining in the United States into midlife and older adulthood may be vulnerable to heightened prevalence of disability.