There is emerging evidence that Christian undergraduates can be stigmatized in undergraduate biology classrooms. This stigma seems to stem from the secular culture of biology and may be affected by instructor identity as most biology instructors are non-religious, but no studies have examined the impact of instructors revealing that they are religious. We used social identity theory to guide an investigation of student perceptions of an instructor candidate-for-hire revealing a Christian identity while teaching evolution. Students were randomly assigned to watch one of two lecture videos that differed only in whether the instructor actor revealed as Christian or non-religious. Students were then surveyed about their perceptions of the instructor's decision to reveal. We found that when students' Christian or non-religious identity aligned with the Christian or non-religious identity of the instructor, students perceived that the instructor revealing increased how approachable and inclusive she seemed. Identity alignment increased Christian and non-religious students' sense of belonging in the scientific community, but identity misalignment reduced belonging for some Christian students viewing a non-religious instructor and had no impact for most non-religious students viewing a Christian instructor. Many students, especially those whose identities aligned with the instructor, reported that the instructor revealing her identity normalized their perception of that identity in science. When an instructor revealed as Christian, most students did not feel as though their perceptions of instructor competence were affected, but many students thought the non-religious instructor's decision to reveal made her seem more competent. Our findings add to our understanding of how student-instructor identity alignment can affect the experiences of college students.