The aim of this systematic review was to determine the quality and comprehensiveness of guidelines developed for employers to detect, prevent, and manage mental health problems in the workplace. An integrated approach that combined expertise from medicine, psychology, public health, management, and occupational health and safety was identified as a best practice framework to assess guideline comprehensiveness. An iterative search strategy of the grey literature was used plus consultation with experts in psychology, public health, and mental health promotion. Inclusion criteria were documents published in English and developed specifically for employers to detect, prevent, and manage mental health problems in the workplace. A total of 20 guidelines met these criteria and were reviewed. Development documents were included to inform quality assessment. This was performed using the AGREE II rating system. Our results indicated that low scores were often due to a lack of focus on prevention and rather a focus on the detection and treatment of mental health problems in the workplace. When prevention recommendations were included they were often individually focused and did not include practical tools or advice to implement. An inconsistency in language, lack of consultation with relevant population groups in the development process and a failure to outline and differentiate between the legal/minimum requirements of a region were also observed. The findings from this systematic review will inform translation of scientific evidence into practical recommendations to prevent mental health problems within the workplace. It will also direct employers, clinicians, and policy-makers towards examples of best-practice guidelines.