Prior correlational studies have shown that belief in the biological theory of sexual orientation (BTSO) is associated with more positive attitudes toward homosexuality. However, individuals often interpret scientific evidence in ways that align with their pre-existing beliefs and motivations. This research experimentally investigated whether gender and religiosity moderate heterosexual individuals' responses to scientific evidence either supporting or refuting BTSO. In two studies, heterosexual men (Study 1, N = 118) and both men and women (Study 2, N = 280) reported their religiosity and were exposed to evidence suggesting either biological differences or similarities between heterosexual and gay individuals. Results showed that, in the biological differences condition, heterosexual women and less religious men were more likely to perceive homosexuality as a natural biological variation and expressed more positive attitudes toward it. In contrast, more religious men interpreted the same evidence as indicating a biological anomaly in gay individuals and displayed more negative attitudes toward homosexuality.