The purpose of this study was to determine the efficacy of a peer-led illness self-management intervention called Wellness Recovery Action Planning (WRAP) by comparing it with usual care. The primary outcome was reduction of psychiatric symptoms, with secondary outcomes of increased hopefulness, and enhanced quality of life (QOL). A total of 519 adults with severe and persistent mental illness were recruited from outpatient community mental health settings in 6 Ohio communities and randomly assigned to the 8-week intervention or a wait-list control condition. Outcomes were assessed at end of treatment and at 6-month follow-up using an intent-to-treat mixed-effects random regression analysis. Compared to controls, at immediate postintervention and at 6-month follow-up, WRAP participants reported: (1) significantly greater reduction over time in Brief Symptom Inventory Global Symptom Severity and Positive Symptom Total, (2) significantly greater improvement over time in hopefulness as assessed by the Hope Scale total score and subscale for goal directed hopefulness, and (3) enhanced improvement over time in QOL as assessed by the World Health Organization Quality of Life-BREF environment subscale. These results indicate that peer-delivered mental illness self-management training reduces psychiatric symptoms, enhances participants' hopefulness, and improves their QOL over time. This confirms the importance of peer-led wellness management interventions, such as WRAP, as part of a group of evidence-based recovery-oriented services.