Company innovation strategies have recently been characterized by a trend towards more collaboration, through the sharing of ideas, knowledge, and expertise across firms' or industries' boundaries. Innovation clusters are considered as privileged places for collaborative innovation to develop. A recent stream of literature highlights the key role of cluster governance in facilitating and promoting these collaborative dynamics. However, little is known about the practices of cluster governance for managing knowledge at the cluster level although it is considered as a key determinant of cluster's competitiveness. This research focuses on knowledge brokering activities implemented in this inter-organizational context, showing how they cross knowledge boundaries and structure open innovation dynamics. The concept of broker has been studied through network studies and innovation studies; Our aim is then to compare knowledge broker activities at the governance level in different clusters in France in order to highlight their differentiated impact on open innovation dynamics.