Prior research on the participation in intergroup conflict suggests that prosocial individuals are parochial cooperators who escalate intergroup conflict. However, evidence on this conjecture is currently inconclusive. We provide a critical empirical test of the link between individuals’ prosocial tendencies (operationalized via Social Value Orientation [SVO] and trait Honesty-Humility) and cooperative behavior in different intergroup conflict games (i.e., variants of the Intergroup Prisoner’s Dilemma). Contradicting the view that prosocial individuals fuel intergroup conflict, both trait dimensions were positively associated with cooperative behavior toward others in general, irrespective of others’ group membership. That is, individuals with a prosocial SVO or high levels of Honesty-Humility, respectively, refrained from harming out-group members and, if possible, even benefited them. Overall, the results imply that the cooperativeness of prosocial individuals is universal in nature, thus exceeding the in-group boundary. Prosocial individuals are hence willing to foster intergroup cooperation rather than fueling intergroup conflict.