Background/Objectives: Recovery is a deeply personal, unique process of clients themselves. How can professionals support this recovery process? This study focuses on the effectiveness of a collaborative long-term training program. Methods: Using quantitative data from a longitudinal study of recovery, the changes in knowledge and attitudes towards recovery of mental health professionals were explored. By using a stepped wedge trial design, 210 professionals and 142 clients filled in two questionnaires five times within two years. In this study, the professionals filled in a 5-item Dutch version of the „Recovery Attitudes Questionnaire“ (RAQ-7) and 14 items of the „Recovery Knowledge Inventory“ (RKI). The RAQ measures the attitudes towards recovery within mental health care providers. The RKI measures knowledge about recovery and recovery processes. The clients filled in the „Mental Health Recovery Measure“ (MHRM) and the „Recovery Promoting Relationship Scale“ (RPRS). The MHRM is a 30-item questionnaire designed to comprehensively assess the recovery process for individuals with serious mental illness. The RPRS is a 24-item scale that measures the generic components of mental health providers’ recovery-promoting professional competence. Results: Results show a positive change in attitudes after two years of education. A positive result about knowledge towards recovery was seen after the first intervention but disappeared after the second intervention. Preliminary data showed no effect on client outcomes. Further analyses of follow-up data will be presented. Discussion/Conclusions: The results support the effectiveness of a recovery training program for professionals on attitudes towards recovery.