New technologies, such as cleantech, are frequently heralded as uniquely positioned to address complex socio-environmental challenges and contribute to facilitating “just” energy transition within and among nations. Building on a relational perspective of technology, we develop theory that explains how intermediary-led market-making processes enable and disable the multiple affordances of cleantech and other similarly promising “green” technologies. More specifically, we theorize how market intermediaries, by brokering the varying temporal and competitiveness imperatives of actors involved in market-making processes, create market opportunity structures that erode the ethical affordances of these technologies and thus diminish their potential for realizing just energy transition. Our insights raise important questions about the limits of markets for addressing the looming climate emergency.