In this paper we explore how blockchain and smart contracts can build trust and act as catalysts for sustainable social businesses by supporting the coexistence of social and economic logics of social ventures. To achieve this we draw upon Yunus’ seven principles of social business to present six emergent questions challenging how blockchain can improve the sustainability of social ventures and support the fulfilment of the principles. Our contribution is a social business blockchain model, codifying Yunus’ principles as smart contract functions, offering novel insights into how blockchain could be utilised to promote the coexistence of social and economic logics (i.e. the defining characteristics of a social business). In addition, it demonstrates that implementation of this technology elicits new types of trust relationships between stakeholders, social businesses and the blockchain, which can be facilitated through the use of smart contracts.