BACKGROUND: Participation in mental health system strengthening by people with mental health problems and their families is a cornerstone of people-centred mental health care, yet there is a dearth of research about participation from low- and middle-income countries (LMICs), particularly from the Asia Pacific region. Hence, this study aimed to assess the current situation, challenges, enabling factors and future actions for service user and family participation in mental health policy making in Timor-Leste. METHODS: In-depth interviews were conducted with 85 adults (≥18 years) who were: (1) mental health service users (n = 20) and their families (n = 10); (2) government decision makers (n = 10); (3) mental health and social service providers (n = 23); (4) civil society (n = 9); and (5) other groups (n = 13). Interview data was analysed using framework analysis. RESULTS: There was limited service user, family and community participation in mental health policy making in Timor-Leste. Perceptions that policy making is a technical exercise and that people with mental health problems lack cognitive capacity, and a lack of supportive mechanisms challenged participation. Enabling factors were a strong focus on human rights within the social sector, and existing mechanisms for advocacy and representation of people with disabilities in social policy making. Participants suggested bolstering civil society representation of people with mental health problems, and increasing mental health awareness and literacy, including government competencies to facilitate service user participation. CONCLUSION: The findings highlight the need for theoretical and practical focus on the role of family within mental health system development in LMICs. Global mental health research and practice should adopt a critical approach to mental health service user and family participation to ensure that the concept and strategies to achieve this are embedded in LMIC knowledge.