Introduction: There are over 43,000 occupational therapists across the United Kingdom, with mental health occupational therapists being acknowledged as a main workforce of OT services. However, staff shortages are occurring, and urgent action is needed to retain this important workforce. Methods: The systematic literature search was conducted in the CINAHL, PsycINFO and Scopus databases to identify research literature published since 2008. Due to the heterogeneity of the included studies, a narrative synthesis was utilized. Results: A total of 20 studies (21 papers) were included in the review. Five thematic factors – well-being at work, organizational work environment factors, job resources, supervision and staffing, along with various subtheme factors emerged from the synthesis. The findings suggest that retaining mental health occupational therapists is a complex issue, affected by many factors. The study emphasizes the triangular relationship among three aspects of well-being (job satisfaction, professional identity and burnout) at work and introduces the concept of a ’Retention Ecosystem’. This illustrates how subtheme factors interconnect and influence the retention of mental health occupational therapists. Conclusion: The retention of mental health occupational therapists is revealed to be a multifaceted challenge. There is a need for developing more targeted, meaningful and holistic strategies for retaining the current mental health occupational therapist workforce.