Changes in mental health provision have led to practitioners and service providers reviewing how they incorporate service users in assessment processes and treatment decisions. Case formulation (CF) is a framework that informs a choice of psychological treatments providing a bridge between assessment and treatment phases to guide treatment options. However, CF is not routinely practised in mental health; hence this paper reviews CF literature to establish its efficacy for service users experiencing mental health issues. The purpose of this study is to assess the efficacy, reliability and validity of CF and its process and function in providing treatment for service users experiencing mental health issues and to explore practitioner training requirements. A systematic search of English language publications on CF and treatment frameworks from 1999-2011 was conducted searching electronic databases. Additionally, two seminal pieces of CF work were included. The findings demonstrate evidence of CF's efficacy and suggest practitioner training programmes to increase professional expertise and enhance service user outcomes. However, limited evidence exists and further research is required to address efficacy and training implications of CF.