The cocoa sector faces a number of deeply embedded, interrelated challenges, including old trees with low productivity; low farmer and worker incomes; pest and disease attacks; political instability in many of the main countries of origin; persistent poor labour conditions and negative environmental impacts, such as deforestation, soil degradation and pollution; tight relationship between supply in the face of growing demand and longterm cyclical recession and expansion booms affecting global market and farm gate prices (Ruf and Siswoputranto 1995; Nkamleu et al. 2010; Matissek et al. 2012; Fountain and HutzAdams 2015). Organising smallholders into groups and undertaking voluntary initiatives, such as certification, often accompanied by training and improved access to agricultural inputs, have been proposed to address some of these multiple, long-running problems. These sustainability interventions have been implemented largely by international traders in the cocoa value chain, government agencies, certification organisations and nongovernmental organisations (NGOs). But do they work? What has been the impact of the multitude of sustainability-based interventions in the last decade on different types of farmers, and how to untangle the impacts of different interventions?