The search for legitimacy is essential for all emerging companies in order to acquire resources. However, in the case of university spin-off, legitimacy must be sought from multiple stakeholders with different expectations. It also must be dealt with in all of its dimensions. The theoretical framework of legitimacy helped us to understand the reasons why the launch of a university spin-off might fail. A longitudinal and in-depth case study provide insights into previously unknown dynamics of the legitimation process and the impact of the search for legitimacy with different stakeholders on a nascent venture. It shows in particular that the socio-political dimension of legitimacy is central in the case of university spin-offs due to their original link with the university.