A survey experiment, carried out in a field setting among Sunni Arab Syrian refugees ( N = 2,479), examined the effect of exposure to wartime trauma, ethnoreligious group affiliation, and degree of hostility of intergroup relations on altruism and positive emotional regard. The results showed that in-group targets were met with more positive emotional regard and altruism than relatively neutral out-group targets, which in turn were met with more positive emotional regard and altruism than individuals from a hostile out-group. These tendencies were elevated among participants with a high degree of exposure to wartime trauma. Emotions mediated the effect of ethnoreligious group affiliation on altruism, and this mediating effect was moderated by exposure to wartime trauma.