In recent decades, rapid growth of the U.S. Hispanic population has raised concerns about immigrant adaptation, including fertility. Empirical research suggests that Hispanics, especially Mexicans, might not be following the historical European pattern of rapid intergenerational fertility decline (and convergence toward native levels). If confirmed, continued high Hispanic fertility could indicate a broader lack of assimilation into mainstream American society. In this paper, we reexamine the issue of Hispanic and Mexican fertility using an approach that combines biological and immigrant generations to more closely approximate a comparison of immigrant women with those of their daughters’ and granddaughters’ generation. Contrary to cross-sectional results, our new analyses show that Hispanic and Mexican fertility is converging with that of whites, and that it is similarly responsive to period conditions and to women’s level of education. In addition, we employ a mathematical simulation to illustrate the conditions under which cross-sectional analyses can produce misleading results. Finally, we discuss the import of the fertility convergence we document for debates about immigrant assimilation.