Since their emergence almost two decades ago, accelerators have evolved towards a global phenomenon that has the potential to shape global economies and societies. The rapid evolvement of the accelerator phenomenon increasingly caught scholars’ interest to examine what makes this specific form of startup support unique and popular in practice. Despite the growing amount of valuable contributions in accelerator research, several key aspects of the accelerator phenomenon remain unsolved or misunderstood, which leaves scholars as well as practitioners with a discordant understanding of how and why accelerators evolved and how they function to date. Hence, ambiguities are still large with regard to thoroughly understanding the accelerator mechanism and its recent developments. However, this understanding is crucial to develop theory in accelerator research and provide assistance for practitioners on how to increase value creation of accelerator programs. By means of five research studies this cumulative dissertation contributes to the lack of common conceptual foundations, an adequate consideration of theoretical underpinnings, a contemporary presentation of defining accelerator characteristics and their evolvement, and reliable insights on accelerator efficacy. In addition, this dissertation contributes numerous lessons learned and guidance to various stakeholders affected by accelerators.