We use the National Survey of Family Growth to identify race-ethnic differences in nonmarital fertility, paying particular attention to Mexican American women. On the basis of a sample of 9,054 White, Black, and Mexican American women, we use event history methods to explore the role of family background, a woman’s own employment and school enrollment, and cohabitation on nonmarital fertility. We additionally determine whether these relationships vary by socioeconomic background. The above factors are all significantly related to the risk of a nonmarital birth and reduce Mexican American–White differentials. Interestingly, higher fertility within cohabiting unions among Mexican American women, despite lower levels of cohabitation, contributes to their higher nonmarital fertility relative to White women.