Main objectives of this master thesis are to identify best practices contributing to enhancement of performance of start-up accelerators in Europe and US, and to provide recommendations for start-up ecosystem stakeholders in creation of better environment for start-up accelerators creation, and functioning. Authors have decided on international literature review, electronic audit of official websites of start-up accelerators, mystery stakeholder method, and electronic surveys with start-up accelerators- managing teams. While European start-up accelerators basing on Austria and Poland are relatively new form of entrepreneurship support ecosystem, a set of best practices and recommendations for its stakeholders deriving from more mature model in USA can be indicated. Also start-up accelerators based in the US can derive from experience worked out by their European counterparts. In relation to countries investigated, it seems necessary to create instruments fostering start-up accelerators creation by public authorities, as well as to foster dissemination of the best practices between existing start-up accelerators. The originality of this master thesis lies in research of recent, international literature on the subject, and empirical research performed, resulting in variety of idiosyncratic, applicable conclusions for start-up ecosystem stakeholders.