The purpose of this study is to explore critical aspects in the establishment of an open innovation arena. This study considers only the perspective of science parks as the establisher and facilitator of the open innovation arenas. By understanding these critical aspects science parks and its participants can benefit from improved innovativeness. Using existing theories, a theoretical framework illustrating critical aspects for the establishment of an open innovation arena was created and subsequently tested through a qualitative research strategy. The research design included case studies into four science parks, three in Sweden and one in the UK, at various stages of establishing and facilitating open innovation arenas. The primary data comprised interviews with top management at each of the science parks, as well as one interview with a committee overseeing science parks in Sweden. The locations for the case study selection were based on Sweden and United Kingdom’s current prominence and success in fostering collaborations. The results of this study indicate that there are a number of critical aspects important during the establishment of open innovation arenas by science parks. Among these critical aspects are the selection of participants, a neutral and passive stance on formalization of contracts and IP, the creation of trust and motivation within the arena, the importance of the physical arena setting and the benefit of an arena topic area prominent amongst the surrounding participants. In addition, this study shows the importance of science parks’ neutral position, as well as the influence of the participants throughout all aspects. Based on these findings, practical and theoretical implications are presented and discussed in the paper. The key implications of this study are that science parks should play an active role to select appropriate projects and participants in order to create trust and motivation within the arena, provide a physical meeting place and access to specialized equipment that fosters communication and encourages collaboration among participants, as well as sourcing projects close to the science park’s geographical proximity. Additionally, they should choose one or more topic area and utilize networks in order to build up expertise, While science parks should play a passive role regarding formalization and IP regulations, it is important that they know how to assists the participants when requested.