Teams of teams, or multiteam systems, are increasingly used to complete challenging tasks in dynamic environments. Individual teams are integrated in multiteam systems as ‘component teams’ that heavily rely on each other’s inputs, processes, and outcomes to perform effectively and to achieve shared, multiteam system goals. Members need to engage in boundary spanning: actions to establish linkages and manage interactions with other component teams. In this study we consider members’ personalities as antecedents for such boundary spanning behavior. Specifically, we suggest that boundary spanners’ similarity in extraversion communicates a compatible approach to coordination, which elicits boundary spanning and, in turn, enhances perceived boundary spanning effectiveness. Results of a multiteam system experiment confirm these expectations.