Abstract
Volunteer tourism organisations are largely unaccountable for the claims they make about generating benefits from the projects that they sell. The few evaluations of how volunteer tourism projects fail or succeed tend to underestimate the importance of contextual factors affecting the mechanisms introduced to achieve a desired sustainability outcome. Realistic evaluation is a recently developed methodology to critically develop testable context-mechanism-outcome (CMO) propositions that explain what works, for whom, under which circumstances. Our study makes a theoretical contribution by uniquely integrating realistic evaluation with collaboration theory to study the volunteer tourism supply chain, in order to demonstrate how to develop an evaluative framework to map out the components of CMO configurations. Our study also makes a methodological contribution by unpacking the black box of the mechanisms to deliver sustainable change through the supply chain of the volunteer tourism industry, which can be subsequently used to systematically monitor and evaluate context-specific circumstances that affect how different volunteering supply chains affect the sustainability of the projects’ outcomes.