One of the more salient roles of school psychologists is the school-based assessment of child and adolescent mental health problems. The most widely used diagnostic and classification system for mental health disorders in the United States is the Diagnostic and Statistical Manual of Mental Disorders (DSM). Many school psychologists (or their administrators) may believe they are not eligible to provide DSM diagnoses. However, with appropriate training, school professionals can competently and ethically incorporate this tool to benefit students with disabilities, if permitted by state law and local policy. This article will examine whether school psychologists can use the DSM to diagnose students and, if so, whether they should do this and under what circumstances. To address these questions, relevant ethical, legal, and professional issues will be discussed.