Objective. Survey research posits that Mexican Americans’ perceptions of the costs and benefits of immigration drive their opinions about immigration, but this re- search does not provide a clear picture of how Mexican Americans calculate these costs and benefits. This article aims to understand the processes that explain how Mexican Americans calculate the costs and benefits of Mexican immigration. Meth- ods. The article employs 123 in-depth interviews and observation with later- generation Mexican Americans in Garden City, Kansas, and Santa Maria, Cali- fornia. Result. Respondents are ambivalent about how Mexican immigrants affect their lives, and their ambivalence is driven by prevailing ideologies in American society regarding immigration, race, and ethnicity. On the one hand, ardent anti- Mexican nativism leads Mexican Americans to see substantial costs accruing to Mexican immigration. Mexican Americans fear that anti-Mexican nativism leads to status degradation for all people of Mexican descent. On the other hand, an ideology of multiculturalism and its accompanying value of diversity lead Mexican Americans to see substantial benefits accruing to the large Mexican-immigrant population, par- ticularly in politics, the labor market, and popular culture. Conclusions. Mexican Americans’ perceptions of the costs and benefits of Mexican immigration are based not only on economic considerations, but on social and cultural considerations structured by prevailing and often paradoxical ideologies. Respondents’ structural position increases concerns about status degradation resulting from immigration, but also shapes how they are positioned to benefit from the boost in prominence that immigration provides to the entire Mexican-origin population.