Adolescence is an important developmental stage in which lasting patterns of health and wellbeing are established (Sawyer et al., 2012). Due to the social, mental and physical changes that occur during this transitional period, adolescence is regarded as a time of increased sensitivity and vulnerability, with research suggesting that mental health issues surge during the adolescent period (Schwarz, 2009; Malla et al., 2018). Epidemiological evidence from both national and international research suggests that adolescent mental health and wellbeing has deteriorated significantly over the last two decades (Cosma et al., 2020; Centre for Disease Control, 2020). There is widespread concern that this decline in youth wellbeing has been exacerbated by the Covid-19 pandemic (Fegert et al., 2020). Mental health problems can have a severe impact on the social and emotional development of the young person, are linked to poorer long-term health, and are also a major risk factor for suicidal behaviour (Collishaw & Sellers, 2020; Patel et al., 2018). Public health professionals and policy makers have identified the need to respond to this decline in youth mental health as a public health priority (Collishaw & Sellers, 2020). In Ireland, youth mental health is widely recognised as an area in need of increased policy focus, with Better Outcomes, Brighter Futures, the National Policy Framework for Children and Young People 2014–2020, acknowledging the importance of integrated policy solutions to promote youth mental health and wellbeing. In recent years, it has been increasingly recognised that while clinical interventions are important and necessary, young people with mental health needs may also benefit from community intervention and support (Hart et al., 2021). Young people experiencing mental health issues may become isolated from their peers and community and may have few opportunities to interact socially with others or may find these interactions challenging. It is argued that community and social networks have the potential to enrich the lives of young people experiencing mental health issues and provide multiple layers of support to help address problems or difficulties. In the context of youth mental health, community services have been found to aid recovery and promote wellbeing (De Wit et al., 2016; Jorm, 2012) and may help to relieve the pressure on primary and secondary care services (Chatterjee et al., 2017). Youth mentoring is a community-based intervention which can help extend the reach of psychological support for young people and is a potentially powerful tool for the prevention of and intervention in youth mental ill-health (Cavell et al., 2021; DuBois et al., 2018a; Hart et al., 2021; Munson & Railey, 2016). Youth-mentoring programmes create a ‘match’ or relationship between a young person and a volunteer mentor and they meet weekly for a year or more. The youth-mentoring model recognises that many young people benefit from support and friendship from a caring adult outside of their family and peer group (Dolan and Brady, 2012). Research has indicated that youth who participate in mentoring programmes, such as Big Brother Big Sister (BBBS), show improved social, emotional, cognitive and behavioural outcomes (Goldner & Ben-Eliyahu, 2021). The national youth organisation Foróige has been operating the BBBS youth-mentoring programme in Ireland since 2002. A Randomised Control Trial (RCT) evaluation of the programme in Ireland found evidence of enhanced emotional wellbeing and perceived support among young people participating in the programme (Dolan et al., 2011). In Ireland, the Health Service Executive (HSE) Child and Adolescent Mental Health Service (CAMHS) is responsible for the provision of youth mental health services. In 2018, CAMHS entered a partnership with Foróige’s Big Brother Big Sister programme with the aim of facilitating access to youth-mentoring relationships as an additional support for young people attending or exiting CAMHS. It was envisaged that the mentoring relationships would help young people to build and develop protective factors, such as emotional resilience, self-esteem, positive social networks and community engagement, while also building capacity to address risk factors, such as bullying (Foróige, 2018). The partnership arose in the context of the HSE National Service Plan (2018), which aimed to improve access for young people to appropriate locally based early intervention and prevention services. The purpose of this study is to examine the working partnership between CAMHS and the Foróige BBBS mentoring programme and explore the value of youth mentoring from the perspective of multiple stakeholders, including youth, parents/ guardians, BBBS mentors, BBBS staff and CAMHS staff. As part of the study, 40 participants (10 mentors, 10 youth, 10 parents/guardians, 10 staff) took part in semi structured qualitative interviews exploring their experiences and opinions of the BBBS mentoring programme. Results indicated that young people typically developed trusting, empathic friendships with their mentors, with participants identifying several factors which they believed influenced the strength of the mentoring bond which developed. Participants typically regarded the BBBS programme as a beneficial resource for young people and their families, with programme participation frequently linked to positive social–emotional, identity and cognitive development. While certain programme features, such as the provision of support from a non-familial adult, were frequently commended by participants, participants also made recommendations for how the BBBS programme and/or its relationship with CAMHS could be enhanced. Overall, the findings from this report provide unique insights into the utility of youth mentoring as an additional supportive resource for young people involved with mental health services, and have notable implications for research and practice. We would like to acknowledge the Health Service Executive for funding this research. non-peer-reviewed