Tbis paper explores tbe development of green entrepreneursbip and its potential role in transformative cbange towards a green economy. It achieves tbis tbrougb a study of tbe green building sector in England and Wales, based on qualitative empirical data from fifty-five semistructured interviews witb businesses in tbe green building sector and witb support organisations, including banks, financial sources, and business advice and support. Tbe paper both critiques and syntbesises two bodies of literatureentrepreneurial researcb and sociotecbnical transitions theories, specifically tbe multilevel perspective (MLP)-to better understand tbe role of green entrepreneurs in facilitating a sbift towards a green economy. Tbis analysis embeds green entrepreneurs in a wider system of actors, ratber tban reifying tbe lone entrepreneurial bero, in order to explore bow green entrepreneurs facilitate sustainability transitions. Tbe paper cballenges tbe notion tbat green entrepreneurs are an unproblematic category. We discovered tbat individuals move between 'green' and 'conventional' business, evolving over time, sucb tbat tbis is a fiuid and blurred, ratber tban static, state. Moreover, wbile tbe green economy and tbe green building sector are often referred to as coherent sectors, witb agreed and consistent practices, our evidence suggests tbat they are far from agreed, tbat business models vary, and tbat tbere are significant contradictions within so-called green building practices. Tbe paper contributes to tbe development of sociotecbnical transitions tbeory and suggests tbat tbe MLP needs to incorporate complexity and multiplicity witbin nicbes, tbat niches may be inberently conflictual ratber tban consensual, and tbat tbe concept of 'protection' for nicbes is problematic.