Objectives Individuals employ causal reasoning to explain the world around them, including political events, group behavior, and conditions in society. People may attribute causes of behavior to controllable components, such as individual choices, or uncontrollable elements, such as broader forces in the environment. To this, we add biological or genetic attributions that have received increasing attention. Broadly, we argue that people's understanding about genetics as a cause for group behavior influences perceptions of immutability and stereotypical judgments about groups. Methods Making use of individual‐level data from three national surveys of American adults, we examine causal beliefs about the origins of homosexuality. Specifically, we assess the impact of genetic attributions on judgments about whether a gay or lesbian person's sexual orientation can or cannot be changed. We also examine the association between genetic attributions and several stereotypic judgments about gays and lesbians. Results We find that genetic attributions strongly shape perceptions of immutability as well as stereotypic judgments about gays and lesbians. Conclusions Implications of our findings for attribution theory and the attitudinal changes that follow from the public's understanding of genetics and its impact on sexual orientation are discussed.