Technology transfer offices (TTOs) play an important role in innovation ecosystems. There is a global strive to make these offices more efficient and improve their performance. This study aims to reason the key factors influencing the performance of TTOs at the members of the European Consortium of Innovative Universities (ECIU). To reach this aim, the comparative literature review of the factors influencing the performance of the TTOs was performed first. The survey along with the semi-structured interviews interviewing leaders of the TTOs with the aim to validate the relevance of the factors was conducted afterwards. The discussion on the key factors influencing the performance of TTOs at ECIU members is presented at the end of the study. The study reveals the following as the key factors influencing the performance of TTOs at the ECIU network: i) TTO strategy; ii) relationships with investors; iii) networking; iv) functioning of a special TTO unit dedicated to working with industry; and v) business experience of TTO staff. It also brings an extension to the technology transfer literature by discussing organizational issues of technology transfer in the European context. The study reveals that the key factors influencing the performance of TTOs at ECIU members are quite similar regardless of the age of TTOs or the country of operation.