There is growing debate over whether applications of blockchain and other financial technologies (‘fintechs’) reinforce forms of neo-colonial extraction that perpetuate North–South inequities or help enact decolonial ambitions across the Global South. This paper expands such discussions and contributes to this special issue on ‘fintech in Africa’ by situating emerging African blockchain techno-experimentation within wider international infrastructural relations. We argue that blockchain-based activities in and across the African continent must be understood within those also unfolding in countries that have been subjected to financial sanctions of varying types (China, Iran, Russia, Venezuela) by the European Union, United States, and United Nations. Our analysis traces how blockchain-based applications by sanctioned countries are extending exclusions in novel and existing socio-technical relations. We conclude that blockchain-based experiments are facilitating rather than displacing a colonial finance/security infrastructure.