Does gender composition affect a group’s willingness to cooperate with another group? We studied this question by examining 188 three- and four-person groups of master-level business students (N = 682) playing a multiple-round intergroup prisoner’s dilemma game. The proportion of male group members was positively related to the rate of initial cooperation. However, the proportion of female group members was positively related to an increase in cooperation when, later in the game, group representatives were given the chance to communicate face to face. No gender effects related to cooperation were found among the participants as a consequence of an unexpected prolongation of the game. In particular, all-female groups seemed to differ from all the other gender compositions; initially, they were very competitive, but they also became very cooperative after face-to-face communication between group representatives.

Keywords: gender, group composition, cooperation, prisoner’s dilemma, intergroup