Intermediaries are actors who perform several functions during innovation processes such as brokering and networking. In this article, the aim is to analyse how intermediaries support collaborative innovation processes taking place in green maritime technology projects. In particular, retrofit projects related to cleaner technologies and small vessels are an understudied subject. The case study of a Danish small island ferry retrofit shows that intermediaries are important to stage the collaboration between actors. They can provide functions to the incipient network as foresight, brokering, increasing network connectivity, and scanning of information. However, intermediaries can also have a proactive role in shaping the emerging innovation pathways. In this case study, intermediaries negotiate each partner's role and define the goals of the project. The results contribute to the broader eco-innovation literature by analysing intermediation in innovation in a process perspective.