<p>Despite abundant research pertaining to green start-up generation has acknowledged influences of environmental technology, insufficient attention has been paid to how environmental technology structures facilitate green start-up emergence. Therefore, to fill this gap, we investigate how environmental technological specialization and diversification affect the emergence of green start-ups, considering the role of both technological opportunities and environmental regulation. Our findings suggest that while specialization limits entrepreneurial entry due to its narrow focus, path dependence, and intense competition, diversification promotes it by providing complementary, collaborative, and alternative technologies, as well as creating broader opportunities. We also find technological opportunities mediate green technology structures and green start-up emergence through knowledge spillovers. Moreover, environmental regulation curbs diversification and green start-up entry. However, due to the fact that green entrepreneurship derived from specialization is more experienced in evading environmental regulatory penalties, environmental regulation does not benefit specialization and green start-up entry. This article offers a new entry point for the study of the relationship between environmental technology and the generation of green start-ups and provides fresh perspectives for the application of the knowledge spillover theory of entrepreneurship and institutional theory. It also has guiding significance for promoting the commercialization of environmental technology and green entrepreneurship.</p>