Studies have shown that intergroup conflict may result from two distinct human motives: the desire to obtain personal retributions from conflict ( egoism), and the desire to sacrifice for the benefit of the ingroup ( parochial altruism). Yet, the relative strength of these motives is open to debate. In this study, we compare behaviors in two Intergroup Prisoner’s Dilemmas (IPD), which respectively capture altruistic and egoistic motives to generate conflict. Egoistic motives result in about 40% more conflict than altruistic motives. Yet, parochial altruism generates more conflict when three conditions are gathered: i) other ingroup members are parochial altruists, ii) the outgroup is aggressive and iii) the outgroup is rich. Implications regarding the diverging structural causes of terrorism and civil wars are discussed.