This master thesis presents an explorative analysis of how organizational openness is inter- organizationally constituted through communication. Drawing on a Luhmannian communication perspective, I consider decision communication to be the key characteristic of organizations. I theoretically conceptualize organizational openness by using the three- dimensional framework developed by Dobusch et al. (2017a) considering range of purposes, topics, and participants acknowledged as meaningful for organizational decision-making. Seeing an inter-organizational arrangement as catalyst of organizational openness, I explore the arrangement of the Medicines Patent Pool within the pharmaceutical industry as an extreme case to analyze how organizational openness is enabled through inter-organizational closure. By using an adapted framework of (inter-)organizational openness, I show which inter- organizational, mainly formalized, decisions have limit setting, limit softening, and limit restricting influences on organizational openness. Further, I demonstrate how a formal intermediating instance facilitates the emergence and stabilization of this inter-organizational (openness) arrangement.