Abstract Background Gypsy/Travellers have poor health and experience discrimination alongside structural and cultural barriers when accessing health services and consequently may mistrust those services. Our study aims to investigate which approaches to community engagement are most likely to be effective at enhancing trust between Gypsy/Travellers and mainstream health services. Methods This multi-method 30-month study, commenced in June 2015, and comprises four stages. 1. Three related reviews: a) systematic review of Gypsy/Travellers’ access to health services; b) systematic review of reviews of how trust has been conceptualised within healthcare; c) realist synthesis of community engagement approaches to enhance trust and increase Gypsy/Travellers’ participation in health services. The reviews will consider any economic literature; 2. Online consultation with health and social care practitioners, and civil society organisations on existing engagement activities, including perceptions of barriers and good practice; 3. Four in-depth case studies of different Gypsy/Traveller communities, focusing on maternity, early years and child dental health services. The case studies include the views of 32–48 mothers of pre-school children, 32–40 healthcare providers and 8–12 informants from third sector organisations. 4. Two stakeholder workshops exploring whether policy options are realistic, sustainable and replicable. Case study data will be analysed thematically informed by the evaluative framework derived from the realist synthesis in stage one. The main outputs will be: a) an evaluative framework of Gypsy/Travellers’ engagement with health services; b) recommendations for policy and practice; c) evidence on which to base future implementation strategies including estimation of costs. Discussion Our novel multi-method study seeks to provide recommendations for policy and practice that have potential to improve uptake and delivery of health services, and to reduce lifetime health inequalities for Gypsy/Travellers. The findings may have wider resonance for other marginalised populations. Strengths and limitations of the study are discussed. Trial registration Prospero .