Two studies examined the relationship between collective narcissism—an emotional investment in an unrealistic belief about the greatness of an in-group (Golec de Zavala, Cichocka, Eidelson, & Jayawickreme, 2009) — and anti-Semitism in Poland. The results indicate that this relationship is simultaneously mediated by (a) a belief that the in-group is constantly threatened by hostile intentions of other groups (Polish siege beliefs; Bar-Tal & Antebi, 1992a, 1992b) and (b) a belief that the Jews are a particularly threatening out-group because they secretly aim to dominate the world (the conspiracy stereotype of Jews; Bergmann, 2008; Kofta & Sedek, 2005). These results confirm that collective narcissism predicts prejudice against social groups perceived as threatening. Collective narcissists’ sensitivity to intergroup threat is composed of beliefs about vulnerability of the in-group and hostility of the out-group.