BackgroundAlthough the Scottish Government's 2008 national drugs strategy (Road to Recovery) and HM Government's 2017 Drug Strategy emphasise recovery, drug-related deaths continue to increase. An alternative approach is being developed by Independence from Drugs and Alcohol Scotland (IFDAS) inspired by the successful drug recovery community in San Patrignano, Italy. In contrast to harm-reduction measures, a drug recovery community is a complex psychosocial intervention designed to address the wider social determinants of addiction. We aimed to assess the programme theory of the San Patrignano model to identify key mechanisms and stakeholders' perceptions of mechanisms considered essential to transfer to, and those that need adapting for, the new drug recovery community in Scotland. MethodsThis qualitative study consisted of semi-structured interviews with knowledge-rich stakeholders, purposively sampled from San Patrignano (n=6) or IFDAS (10); observational notes recorded during 10 days' immersion in San Patrignano; and notes from meetings and events in both sites. Stakeholders had professional knowledge in a range of areas including social enterprise, clinical expertise, therapeutic recovery community methods, and government social policy. All qualitative datasets were analysed inductively with findings grounded in the data. We drew on realist principles to analyse the mechanisms of change in relation to context, at both individual and organisational levels. Data synthesis was guided by framework analysis. FindingsSan Patrignano stakeholders reported six mechanisms related to recovery at the individual level (commitment to change, removal from former social environment, communal living, peer mentor with lived experience, structure and routine, meaningful work). Four mechanisms contributed to success at the organisational level (visionary leadership, staff dedication, social enterprise, and adaptable learning organisation). IFDAS stakeholders reported mechanisms being directly transferred (eg, peer mentor with lived experience, social enterprise) and those being adapted for the Scottish context. InterpretationThis is one of the first studies to investigate transferability of a successful drug recovery community across different cultural contexts with the aim to prospectively identify essential mechanisms and adaptations required to enhance implementation of the new intervention in Scotland. This study will also contribute to formulation of generic principles on transferability of successful complex interventions across different sociocultural contexts. FundingUK Medical Research Council and Scottish Government Chief Scientist Office Complexity in Health Improvement programme (MC_UU_12017/14).