School-based mental health (SBMH) research often underplays the crucial role that teachers play in supporting student mental health, even as teachers often find themselves encountering student mental health issues. Further, teachers’ and school-based mental health practitioners’ (SBMHPs) work with shared students has historically tended toward distance rather than collaboration. This article explores the virtual fault line where SBMHPs’ and teachers’ work intersect, concerning student mental health issues. Drawing on qualitative data gathered at three high schools that, to varying degrees, required teachers’ involvement with student mental health issues, this study analyzes the nature of teachers’ work in this area. In particular, the study identifies ways in which teachers provided psychosocial support, as well as how teachers’ and SBMHPs’ work intersected. Findings indicate that uncertainty existed at the three schools about teachers’ involvement with student mental health issues, and that this uncertainty was reinforced by organizational structures that promoted a separation of teaching from SBMH. Implications for practice, professional learning, and research are discussed.