From Roman Catholicism’s early days, Antisemitism was its Original Sin. With its Second Vatican Council Declaration aetate, many would have hoped that the Church buried the demons of Catholic Antisemitism for good. But just how thick is the ice that now separates global contemporary Catholic publics from the temptations of a re-emergence of Catholic Antisemitism? While the study of global Antisemitism received important new and global empirical insights from the ADL (Anti-Defamation League) 100 study (ADL, 2014) covering more than 100 countries, comparative studies on Antisemitism among global Roman Catholics are rather lacking. But Antisemitism is around in the world again, and it does so in staggering proportions. It is thus extremely important in view of Catholicism’s still existing role in Western society to find out whether or not practicing Roman Catholics are an exemption from these trends. Our study focuses on indicators of Antisemitism of entire countries in comparison with their practicing Roman Catholic communities, i. e. those Catholics who attend Sunday Mass regularly, the so-called Dominicantes, which still make up some 45% of the global 1.3 billion Roman Catholics according to our population weighted data. Our study is based on the rigorous statistical analysis of freely available cross-national opinion data sets, using the SPSS XXIV statistical software. Since our freely available global database, the World Values Survey, does not offer better, alternative Antisemitism indicators, we had to rely in our work on the rates of rejection of Jewish neighbors, which explain 56.16% of the variance of the far superior ADL (2014) data series, for which the original interviews and the background variables are unfortunately not freely available to global publics. Our proxy results about the anchoring of in the hearts and minds of active global Catholics, based on World Values Survey and other global opinion data are unfortunately not optimistic and suggest the following tendencies: On a global scale, about one in five practicing Roman Catholics still reject to have a Jewish neighbor, irrespective of all the Church’s teaching on Judaism since the Second Vatican Council; Ceteris paribus, adherence to Catholicism, Orthodox Christianity and Islam all are still to be considered as lamentable and significant drivers of the rate of societal Antisemitism (ADL data) in standard OLS multiple regression analyses; A combined Index, developed for this publication, tells us how well active Roman Catholics, attending Church services each Sunday, accepted Jewish neighbors, secondly, whether active Roman Catholics more accepted Jewish neighbors than the society surrounding them, and third, whether the acceptancy of Jewish neighbors increased or decreased over time. Our data show that among the world’s top performing Roman Catholic active communities we find the Dominicantes in the Czech Republic, United States, United Kingdom, Portugal, and Argentina, while among world’s Catholicism worst Nostra aetate performers we find the active Catholic communities in Spain, Poland, Malta, Slovenia, Mexico, and Slovakia. In those countries, social realities among the active Catholic faithful could not be more distant from the ideas and perspectives, expressed in Nostra aetate. In our inter-religious comparison, we also found that only the Catholic Dominicantes in Argentina and the United States were among the world’s top 10% performers in overcoming Antisemitism, while the Catholic Dominicantes in Venezuela, Bosnia, Nigeria, Slovakia, South Africa and South Korea were among the world’s lamentable bottom 2/3 of communities in overcoming Antisemitism. We also analyzed PEW data on the support or rejection of the Jewish State, and European Social Survey data on the acceptancy of Jewish immigration to Europe among religiously active Roman Catholics in comparison to the respective total populations. We also highlight the drivers of Antisemitism by interreligious comparison, using an OLS regression procedure applied to World Values Survey data and analyze the connections between general religious tolerance and Antisemitism. Efforts of public diplomacy by states, transnational media corporations and transnational centers of higher learning concerned with these developments should be undertaken.