Objective: To compare the mental health and well-being of Mexican immigrants with native-born Mexican Americans living in the Lower Rio Grande Valley of Texas. Methods: A randomly stratified sample of 353 Hispanics aged 45 and older were interviewed. The immigrant group (n = 148) was compared with native-born Mexican Americans (n = 205). Results: The findings showed that the native-born group was not significantly different from the immigrant group on measures of depression, health status, life satisfaction, or self-esteem. The immigrant group was found to report significantly more stress than the Mexican American group. Income, age, gender, and acculturation were significant predictors of well-being, whereas immigration status and years of residency were not. Discussion: The well-being of Mexican immigrants in the United States is confounded by such variables as income, age, gender, and acculturation, along with various other contextual factors that characterize their life experiences in the United States.