Purpose Whether or not to disclose mental illness or mental health issues in the work environment is a highly sensitive dilemma. It can facilitate keeping or finding paid employment, but can also lead to losing employment or to not being hired, because of discrimination and stigma. Research questions were: (1) what do stakeholders see as advantages and disadvantages of disclosing mental illness or mental health issues in the work environment?; (2) what factors are of influence on a positive outcome of disclosure? Methods A focus group study was conducted with five different stakeholder groups: people with mental illness, Human Resources professionals, employers, work reintegration professionals, and mental health advocates. Sessions were audio-taped and transcribed verbatim. Thematic content analysis was performed by two researchers using AtlasTi-7.5. Results were visually represented in a diagram to form a theoretical model. Results Concerning (dis-)advantages of disclosure, six themes emerged as advantages (improved relationships, authenticity, work environment support, friendly culture) and two as disadvantages (discrimination and stigma). Of influence on the disclosure outcome were: Aspects of the disclosure process, workplace factors, financial factors, and employee factors. Stakeholders generally agreed, although distinct differences were also found and discussed in the paper. Conclusion As shown from the theoretical model, the (non-) disclosure process is complex, and the outcome is influenced by many factors, most of which cannot be influenced by the individual with mental illness. However, the theme 'Aspects of the disclosure process', including subthemes: who to disclose to, timing, preparation, message content and communication style is promising for improving work participation of people with mental illness or mental health issues, because disclosers can positively influence these aspects themselves.