A significant proportion of undergraduates report having mental health concerns (MHC), which are associated with reduced academic success. Students with MHC are encouraged to seek help from their instructors but may not because of perceived negative reactions by instructors and peers. This suggests stigma about MHC may differentially impact disclosure perceptions of students with MHC compared with their peers, yet the perceptions of both groups have been unexplored. This study surveyed students with and without MHC in the same classes about their hypothetical disclosure of MHC. Students in several introductory biology classes were asked whether they identified as having MHC, whether they would or would not hypothetically disclose MHC to an instructor, and why. Thematic analysis identified reasons underlying their disclosure choices, which were sorted into the three beliefs of the Theory of Planned Behavior: attitudes, subjective norms, and behavioral control. Of the 803 respondents, 50% self-identified as having MHC. Students with MHC were less likely to say they would disclose their MHC to an instructor than students without MHC. Students with and without MHC who said ‘yes’ to disclosure gave similar reasons aligned with attitude beliefs. Students with MHC who said ‘no’ to disclosure perceived that the instructor wouldn’t care (attitude beliefs). Students without MHC who said ‘no’ to disclosure talked more about keeping their MHC private (subjective norms beliefs). Students without MHC who said ‘it depends’ talked more about impact on their course performance (attitude) than students with MHC. This research indicated that students with and without MHC do perceive disclosure differently and suggested that students with MHC focus more on negative instructor reactions, while those without MHC focus on privacy and performance. These differential perceptions may contribute to students with MHC seeing disclosure as a negative social cost versus a positive academic benefit.