Researchers have shown that peer support services as well as the utilization of evidence-based practices (EBPs) contribute significantly to mental health recovery. However, there has been no research to date that has examined the attitudes of mental health peer supports toward EBPs. The purpose of this nonequivalent comparison group, posttest-only study was to test the theory of innovation diffusion and to examine whether different levels of peer support in the implementation of a specific EBP—the Wellness Management and Recovery (WMR) program—influenced their attitudes toward the program. Survey data were collected from 99 peer supports (a) affiliated with a community mental health center, whose members were WMR-certified or (b) affiliated with a consumer-operated services (COS) agency, whose members were WMR-certified, or (c) who were neither WMR-certified nor involved in its implementation. The survey included the Evidence-Based Practice Attitude Scale, which generated four dependent-variable subscale scores related to the theory of innovation diffusion: requirements, appeal, openness, and divergence. Analysis included a series of ANOVAs to examine differences in attitudes based on the level of involvement in the implementation of the WMR emerging best practice. Results indicated that peers involved in the training and implementation of the best practice at COS agencies had more favorable attitudes toward the EBP than peers trained at clinical agencies or peers not involved in implementation. Implications for positive social change include enhanced treatment outcomes—particularly in a COS setting—for persons with psychiatric illness by combining an EBP with peer support.