Large collectives (e.g., organizations, political parties, nations) are seldom unitary players. Rather, they consist of different subgroups that often have conflicting interests. Nonetheless, negotiation research consistently regards negotiating teams, who represent these collectives, as monolithic parties with uniform interests. This article integrates concepts from social psychology, management, political science, and behavioral game theory to explore the effects of subgroup conflict on team negotiation. Specifically, the present research introduced a conflict of interests within negotiating teams and investigated how this internal conflict affects the outcome of the negotiation between teams. An experiment with 80 four-person teams found that conflict between subgroups had a detrimental effect on the performance of negotiating teams. This research also employed a recent model of motivated information processing in groups to investigate possible processes underlying the effect of subgroup conflict on team negotiation.