University spin-off formation can impact local economic growth. This paper addresses the contribution to a university's entrepreneurial support structure by individuals who started a company out of a university. If this contribution is sustainable enough, it may induce a self-amplifying process by which the university's entrepreneurial support-structure is continuously upgraded. Based on a qualitative case study of Leibniz University Hannover, including expert interviews and an in-depth document analyses, it is shown that alumni spin-off entrepreneurs indeed play an important role for a university's entrepreneurial support structure. However, the empirical findings indicate to a differentiation in respect of the nature of such a contribution. While it is an essential ingredient for the realization of particular support measures, it is only a decorative accessory for the evolution of such a structure. The contribution of alumni spin-off entrepreneurs to the upgrade of a university's entrepreneurial support structure leads to the named self-amplifying process.