Background <p>Mental health problems amongst young people in the UK have been rising, yet many still do not receive appropriate support. Involving young people in research can lead to more inclusive services. However, certain groups of young people, including those from ethnic minority backgrounds, lower-income families, refugee, asylum-seeking and other immigrant backgrounds, non-native English speakers, disabled young people and those with long term health conditions remain under-represented in involvement in mental health research. Little research explores the perspectives of these young people on the barriers and enablers to their involvement.</p> Methods <p>This qualitative focus group study used the Behaviour Change Wheel (BCW) and Capability-Opportunity-Motivation model of behaviour (COM-B) to understand influencers on involvement. A group of youth advisors was involved throughout. Five focus groups were conducted, including 18 young people aged 16–25, many from under-represented backgrounds and without previous involvement experience. Thematic analysis was used to categorise barriers and enablers according to the COM-B model and intervention strategies proposed using intervention functions and behaviour change techniques which form part of the BCW.</p> Results <p>Nineteen themes were identified covering all six COM-B domains. Enablers included the perceived value and relevance of the research topic, personal benefits (including financial reward and skill development), as well as safe and inclusive environments where young people of shared experiences come together. Barriers included lack of awareness and access to involvement opportunities, emotional readiness, social norms and the influence of peers. Some barriers were highlighted as particularly relevant to certain groups. Youth advisors provided additional reflections on the findings. BCW informed intervention strategies include proactive outreach efforts, effective preparation of young people (including induction and capacity building), the use of role models and partnership with cultural organisations.</p> Conclusions <p>Many barriers to inclusive youth involvement in mental health research exist. Researchers need to look beyond traditional approaches to include under-represented young people in research. This study highlights enablers that researchers can capitalise on to improve access to involvement opportunities and BCW derived strategies, supported by evidence and young people’s ideas, to overcome barriers. Future research should implement and evaluate these strategies in practice.</p>