Objectives To explore differences in contraceptive use among women of Mexican origin across generations of migration. Methods Logit models were used to assess contraceptive use among 1,830 women of Mexican origin in Cycles 5 (1995) and 6 (2002) of the National Survey of Family Growth (NSFG). Analyses were stratified by age. Initial models controlled for survey year and underlying differences across generations of migration in age and parity; subsequent models added a range of potential mediating variables. Models account for significant interactions between generation of migration and parity. Results Among women under age 30 who have not yet had any children, women in their twenties with parity 3 or more, and women 30 or older with parity 1 or 2, those born in the US are much more likely to use contraception than immigrant women. For other levels of parity, there are no significant differences in contraceptive use across generations of migration. Generational differences in marital status, socio-economic status, health insurance coverage, and catholic religiosity did little to mediate the association between generation of migration and contraceptive use. Conclusions Among women of Mexican origin, patterns of contraceptive use among first-generation immigrants and women of generation 1.5 are similar to those of women in Mexico, with very low rates of contraceptive use among young women who have not yet had a child. Further research is needed to investigate the extent to which this pattern is due to fertility preferences, contraceptive access, or concerns about side effects and infertility. Patterns of contraceptive use appear to change more slowly with acculturation than many other factors, such as education, income, and work force participation.