Introduction Alcohol consumption is a leading cause of mortality, morbidity and adverse social sequelae in Sri Lanka. Effective community-based, culturally adapted or context-specific interventions are required to minimise these harms. We designed a mixed-methods stepped wedge cluster randomised control trial of a complex alcohol intervention. This paper describes the initial trial protocol and subsequent modifications following COVID-19.

Methods and analysis We aimed to recruit 20 villages (approximately n=4000) in rural Sri Lanka. The proposed intervention consisted of health screening clinics, alcohol brief intervention, participatory drama, film, and public health promotion materials to be delivered over 12 weeks.

Following disruptions to the trial resulting from the Easter bombings in 2019, COVID-19 and a national financial crisis, we adapted the study in two main ways. First, the interventions were reconfigured for hybrid delivery. Second, a rolling pre–post study evaluating changes in alcohol use, mental health, social capital and financial stress as the primary outcome and implementation and ex-ante economic analysis as secondary outcomes.

Ethics and dissemination The original study and amendments have been reviewed and granted ethical approval by Rajarata University of Sri Lanka (ERC/2018/21—July 2018 and February 2022) and the University of Sydney (2019/006). Findings will be disseminated locally in collaboration with the community and stakeholders.

The new hybrid approach may be more adaptable, scalable and generalisable than the planned intervention. The changes will allow a closer assessment of individual interventions while enabling the evaluation of this discontinuous event through a naturalistic trial design. This may assist other researchers facing similar disruptions to community-based studies.