Two studies explored how communication within subgroups affected cooperation in a nested social dilemma, in which self,subgroup, and collective interests were opposed. Contributions to the subgroup were higher when communication occurredwithin subgroups than when no communication or communication in the full collective occurred. More importantly, wehypothesized that asymmetric subgroup communication (i.e., when the focal subgroup communicates but the opposingsubgroup does not) would increase subgroup cooperation more than symmetric subgroup communication because thisdifference between subgroups would heighten the salience of the subgroup boundaries, making the subgroup a more likelytarget of group identification. Consistent with this hypothesis, subgroup communication increased allocations to the subgroupthe most when the opposing subgroup did not communicate. We discuss the implications of these results in relation to thesocial dilemma literature.