Antecedents and Consequences of Team Boundary Disagreement (Research Seminar, March 1st, 2004) Mark Mortensen McGill University Abstract Existing research and theory on groups and teams is built on the underlying assumption that the members of teams agree as to who are and who are not their teammates. In a study of 43 software development teams in a large multinational software company, I question this assumption and provide a first examination of the phenomenon of intra-team boundary disagreement and the mechanisms underlying it. I use a web-based survey and semi-structured interviews to identify both antecedents and effects of boundary disagreement. I find evidence that patterns of interdependence and workflow act as antecedents of boundary disagreement, while contrary to my hypotheses, no significant relationship existed between communication patterns and boundary disagreement. I also provide evidence that teams experiencing boundary disagreement perform significantly lower than those without – a relationship mediated by transactive memory, shared team identity, and affective conflict.