Through a historiographical assessment, this article argues that the systematic distinction between religious anti-Judaism and modern anti-Semitism ought to be reassessed and revisited by a study of the Catholic matrix of anti-Semitism. An investigation of this matrix implies a reflection on patterns of continuity as well as on the renewal of prejudice during the interwar period as shown by the case of intransigent Catholic networks under Mgr. Benigni. Bearing witness to an apparently paradoxical mixture of religious, political, and racial prejudices, this type of Catholic anti-Semitism blurs the traditional lines between religious anti-Judaism and modern anti-Semitism. The lingering tradition of religious hostility was reactivated and transformed during the interwar era. After a first reflection on the distinctive features of religious anti-Judaism, this article argues that, far from being exclusive, the Christian and anti-Christian roots of modern anti-Semitism were entwined. Faced with Jewish emancipation, the counter-revolutionary and anti-modern discourse was a middle ground for religious and secular prejudices. A long-term and comparative perspective uncovers the shaping of racial boundaries that challenged religious identities and conversion. Furthermore, fear of the “Judaization” of Christian civilization favored the renewal of Catholic anti-Semitism in the modern context. This allegation of “Jewish infiltration” was also used within the Catholic world, as a weapon against other Catholic rivals.