Collaborating with peers to gain access to knowledge is an attractive alternative for organizations keen to improve their innovativeness, and the rising popularity of open innovation has resulted in the emergence of new actors in the innovation process. Previous research focuses mainly on the firms that collaborate with these actors. This paper adopts the perspective of an open innovation actor and the managerial challenges involved. It is based on a case study of SAFER, a Swedish traffic and vehicle safety research unit with 22 collaborating partners. The unit, which is here called an open innovation arena, differs from an intermediary in that it both enables open innovation within a specific field of expertise and envisages itself as a key player in that same field. The case study reveals three types of challenges for the management of an open innovation arena: challenges that arise at the interface with partner organizations, challenges related to collaboration between the partners, and challenges related to the arena itself.