Purpose – Innovation intermediaries have become key actors in open innovation (OI) contexts. Research has improved the understanding of the managerial challenges inherent to intermediation in situations in which problems are rather well defined. Yet, in some OI situations, the relevant actor networks may not be known, there may be no clear common interest, or severe problems may exist with no legitimate common place where they can be discussed. The purpose of this paper is to contribute to the research on innovation intermediaries by showing how intermediaries address managerial challenges related to a high degree of unknown. Design/methodology/approach – The authors draw upon the extant literature to highlight the common core functions of different types of intermediaries. The authors then introduce the " degree of unknown " as a new contingency variable for the analysis of the role of intermediaries for each of these core functions. The authors illustrate the importance of this new variable with four empirical case studies in different industries and countries in which intermediaries are experiencing situations of high level of unknown. Findings – The authors highlight the specific managerial principles that the four intermediaries applied in creating an environment for collective innovation. Originality/value – Thereby, the authors clarify what intermediation in the unknown may entail.