Three experiments examined the role of intragroup social influence in intergroup competition. In the context of a mutual fate control situation, participants in Experiment 1 demonstrated more intergroup competition in the presence than in the absence of social support for shared self-interest. Experiment 2 revealed that, in the context of a Prisoner's Dilemma Game, this social support effect was stronger when noncorrespondence of outcomes between the interacting groups was low than when it was high. Results from Experiment 3 were consistent with the possibility that the effect of social support is attenuated when noncorrespondence of outcomes is high because under these circumstances intergroup competition is prescribed by a norm of group interest. The implications of these findings for understanding the antecedents of interindividual-intergroup discontinuity are discussed.