Background: In India, heterogenous tribal populations are grouped together under a common category, Scheduled Tribe, for affirmative action. Many tribal communities are closely associated with forests and difficult-to-reach areas and have worse-off health and nutrition indicators. However, poor population health outcomes cannot be explained by geography alone. Social determinants of health, especially various social disadvantages, compound the problem of access and utilisation of health services and undermine their health and nutritional status. The Towards Health Equity and Transformative Action on tribal health (THETA) study has three objectives: (1) describe and analyse extent and patterns of health inequalities, (2) generate theoretical explanations, and (3) pilot an intervention to validate the explanation. Methods: For objective 1, we will conduct household surveys in seven forest areas covering 2722 households in five states across India, along a gradient of socio-geographic disadvantage. For objective 2, we will purposefully select case studies illustrating processes through which socio-geographic disadvantages act at the individual, household/neighbourhood, village or population level, paying careful attention to the interactions across various known axes of inequity. We will use a realist evaluation approach with context-mechanism-outcome configurations generated from the wider literature on tribal health and results of objective 1. For objective 3, we will partner with willing stakeholders to design and pilot an equity-enhancing intervention, drawing on the theoretical explanation generated and evaluate it to further refine our final explanatory theory. Discussion: THETA project seeks to generate site-specific evidence to guide public health policy and programs to better contribute to equitable health in tribal populations. It fulfills the current gap in generating and testing explanatory social theories on the persistent and unfair accumulation of geographical and social disadvantage among tribal populations and finally examines if such approaches could help design equity-enhancing interventions to improve tribal health.