This paper explores how participation in accelerator programs, which are aimed at scaling ventures, influences the self-perceptions of the participants. An entrepreneur’s identity is considered important in both theory and practice, but few studies have investigated how the identities of entrepreneurs/founders are affected by their participation in a program that is aimed mainly at the venture and not the person behind the venture. By providing access to resources, mentorship, and support, which help entrepreneurs test hypotheses and problems, as well as identify markets and business models for their ventures, an accelerator helps entrepreneurs increase their confidence, skills, and knowledge. These factors are important because they enable entrepreneurs to better understand themselves and their perceived opportunity space and choice of actions. Data were collected through in-depth interviews with 14 entrepreneurs that had participated in two different accelerators with slightly different programs. The findings indicate that the accelerators influenced both the personal identify and role identity of the participating entrepreneurs. However, the impact of the accelerator varied according to the self-perceptions of the entrepreneurs’ pre-participation and how far they had come in developing their business concepts. Their admittance to an accelerator in itself boosted their identities. We found no difference between the private accelerator program (PA) and the governmental program (GA). The paper contributes to the literature on entrepreneurial identity formation and the effects of accelerators.