Many manufacturing firms have opened up their product innovation processes and actively transfer knowledge with external partners in the markets for technology. However, the markets for technological knowledge have remained inefficient in comparison with the markets for most products. To reduce some of the market inefficiencies, manufacturing firms may collaborate with innovation intermediaries, which are defined as organizations that act as agents or brokers in the innovation process between two or more parties. These innovation intermediaries comprise different service providers ranging from consulting companies to Internet marketplaces for technology. In light of an increasing importance of intermediary services in the context of open innovation, this paper specifically focuses on the collaboration of manufacturing firms and innovation intermediaries, which may be critical for the success of intermediary services. Based on new interview data from 30 innovation intermediaries and 30 European manufacturing firms, this paper examines the question of how innovation intermediaries and manufacturing firms collaborate concerning the following issues, which emerged as the key themes from the interviews: potential of intermediation, roles of intermediaries, types of intermediation, drivers of intermediation, complementarity of intermediation, compensation of intermediation, and the importance of repeated collaborations. The findings indicate how manufacturing firms may reduce their transaction costs in technology markets by collaborating with intermediaries. However, intermediary services can only be regarded as a complement rather than a substitute of manufacturing firms' internal activities of managing technology transfer. Thus, manufacturing firms need sufficient internal capabilities for managing technology transfer, such as absorptive capacity and desorptive capacity.