Three studies tested whether implicit prototypes about who is authentically American predict discriminatory behavior and judgments against Americans of non-European descent. These studies identified specific contexts in which discrimination is more versus less likely to occur, the underlying mechanism driving it, and moderators of such discrimination. Studies 1 and 2 demonstrated that the more participants held implicit beliefs that the prototypical American is White, the less willing they were to hire qualified Asian Americans in national security jobs; however, this relation did not hold in identical corporate jobs where national security was irrelevant. The implicit belief—behavior link was mediated by doubts about Asian Americans’ national loyalty. Study 3 demonstrated a similar effect in a different domain: The more participants harbored race-based national prototypes, the more negatively they evaluated an immigration policy proposed by an Asian American but not a White policy writer. Political conservatism magnified this effect because of greater concerns about the national loyalty of Asian Americans.