Our aim is to add to the knowledge on a network level, focusing on if, and how, interpartner legitimacy affects the success or failure of network formation and development processes. Existing network theories and research tend to focus on resource exchange rather than on how actors perceive each other in terms of being legitimate or not. The purpose of the article is to analyze the interpartner legitimacy's in?uence on the formation and development processes of regional strategic networks (RSNs) from a network level. Two Swedish cases are discussed in terms of pragmatic, moral and cognitive interpartner legitimacy. The cases and the following discussion illuminate that interpartner legitimacy is important to incorporate into the analytical model if we wish to understand the processes of negotiations on the rules and norms which set the possibilities for survival of multi-actor interactions.