The United Nations’ Sustainable Development Goals have been gaining traction. Green entrepreneurship has emerged as an appealing strategy for governments and educators to address environmental problems. This study examines the determinants affecting the transformation of green entrepreneurial intention into behaviour, a previously unexplored area. Specifically, the moderating roles of sustainability orientation, environmental knowledge, subjective norms, and external institutional support on the effect of green entrepreneurial intention on behaviour are examined. A quantitative survey of 663 Taiwanese individuals was conducted between November and December 2022. The factor structure was evaluated using exploratory factor analyses. The positive relationship between green entrepreneurial intention and behaviour was validated using multiple regression analysis. Environmental knowledge, subjective norms, and external institutional support, but not sustainability orientation, had positive moderating roles. These findings enrich existing theories, including the theory of planned behaviour and social cognitive career theory, and provide practical guidance to educators and policy makers promoting green entrepreneurial action.