Entrepreneurship ecosystems are dynamic local, social, institutional, and cultural processes and actors that encourage and enhance the formation and growth of new businesses. Thus, this study aims to analyze the importance of sustainable urban development in creating favorable urban conditions in the formation of an entrepreneurial ecosystem. Therefore, a qualitative and exploratory study was carried out, operationalized through a case study. The case of the city of Florianópolis (Santa Catarina State, southern Brazil) was studied in depth; it was intentionally selected considering that it has stood out in terms of investments in innovation, technology, and sustainability, in addition to being a reference for quality of life and for its innovation and entrepreneurial ecosystem. It was possible to know the characteristics of the municipality and the main management practices for sustainable urban development developed in Florianópolis. Above all, among the main findings of this study, from the point of view of urban management, we found that the characteristics present in Florianópolis, as a sustainable city, can benefit the development of an entrepreneurial ecosystem. In this way, by investing in management practices for sustainable urban development, the municipality promotes business growth, new technologies, and entrepreneurship, making the territory more attractive to new investments and talent retention. It was possible to find evidence of urban conditions resulting from these practices capable of favoring the creation of an entrepreneurial ecosystem, among which, the following stand out: (1) social integration and articulation between the actors; (2) high quality of life; (3) capital with the highest human development index in the country; (4) a high rate of green areas; (5) enabling legislation for investments; (6) a city where companies open faster in Brazil and 100% digitally. Among this study’s limitations, the complexity of the analyzed phenomenon and amplitude of the context stand out. In addition, the case study method does not allow for a generalization of the results, as they are related to the case of Florianópolis. Despite this, the research presents a large amount of evidence confirming the theoretical assumption of the study, which is: Sustainable urban development creates favorable conditions for the promotion of an entrepreneurial ecosystem in the city of Florianópolis.