Illness Management and Recovery (IMR) is a widely used evidence-based standardized psychosocial intervention. Little is known, however, about the impact of practitioner professional background on the consumer outcome. The current study aims to examine the delivery impact of practitioners who were mental health professionals, peer providers, or paraprofessionals on fidelity and consumer outcome in IMR. Study participants were 252 persons with serious mental illness receiving psychiatric rehabilitation services in the community who received IMR (n = 210) or treatment as usual (TAU; n = 42). Study participants completed IMR groups that were delivered by either mental health professionals (n = 126), peer providers (n = 43), or paraprofessionals (n = 41). Study participants in the treatment group completed the Illness Management and Recovery scale before starting and after completing the IMR program; participants in the control group completed the same scale twice in similar time intervals. Fidelity ratings were made. Regardless of practitioner background, consumers who received the IMR intervention demonstrated significant improvement compared to the control group. Post hoc analyses showed no statistically significant difference on consumer outcome regardless of whether the practitioner was a professional, paraprofessional, or a peer provider. All three IMR groups had good fidelity scores. The results demonstrate that IMR can be implemented with good fidelity and generate positive outcomes when delivered by practitioners who receive sufficient training and supervision regardless of their professional background. PsycINFO Database Record (c) 2013 APA, all rights reserved.