According to the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-5; American Psychiatric Association, 2013), an substance use disorder (SUD) involves patterns of symptoms caused by using a substance that an individual continues taking despite its negative effects. Though there are 11 specific DSM-5 criteria for an SUD, they can be summarized into four main categories: risky use, social problems, physical dependance, and impaired control. Two or three symptoms indicate a mild SUD, four or five indicate a moderate SUD, and six or more symptoms indicate a severe SUD. School psychologists are most likely to encounter students at the experimental stage of substance use, or the mild or moderate level, as a student experiencing a severe SUD is less likely to be attending school due to the impact on functioning and life activities. At this stage, intervention offers an opportunity to prevent heavier use of substances. Increased understanding of current research and practice helps position school psychologists to advocate for supports for students experiencing substance use problems, if not provide direct intervention. To improve outcomes for students, school psychologists must understand recent professional practice paradigm shifts as well as the definition of SUD, the impact of substance use during adolescence, and effective intervention resources.