A major research thrust in science, technology, engineering, and mathematics (STEM) education is focused on how to retain students as STEM majors. The accumulation of seemingly insignificant negative experiences in STEM classes can, over time, lead STEM students to have a low sense of belonging in their disciplines, and this can lead to lower retention. In this paper, we explore how Judeo-Christian students in biology have experiences related to their religious identities that could impact their retention in biology. In 28 interviews with Judeo-Christian students taking undergraduate biology classes, students reported a religious identity that can conflict with the secular culture and content of biology. Some students felt that, because they are religious, they fall within a minority in their classes and would not be seen as credible within the biology community. Students reported adverse experiences when instructors had negative dispositions toward religion and when instructors were rigid in their instructional practices when teaching evolution. These data suggest that this may be a population susceptible to experiences of cultural conflict between their religious identities and their STEM identities, which could have implications for retention. We argue that more research should explore how Judeo-Christian students' experiences in biology classes influence their sense of belonging and retention.