Opioid use disorder (OUD) is increasingly recognized and co-present in patients with cancer. Unfortunately, OUD is not addressed or treated adequately in oncology settings. In addition, patients with cancer-related pain treated with narcotic pain medications are at risk for nonmedical opioid use (NMOU). More than two-thirds of patients with advanced cancer have pain. Both OUD and NMOU need to be concomitantly addressed alongside cancer-related pain management to avoid complications such as overdose. We review the approach to identifying and treating OUD and NMOU in patients with cancer and cancer-related pain.