Although it never entered the Church’s official legal code, the Decretum Gratiani, completed around 1140, systematically summarizes a millennium of ecclesiastical legislature and therefore forms the basis of later canonistic teachings. This applies also to the numerous clauses it contains relating to Jews and Christian-Jewish co-existence. Besides the specific articles that explicitly refer to Jews, importance must be assigned to numerous others which, though they do not expressly name Jews, relate equally to them, and have scarcely been considered in previous analyses. In fact, historical research has also overlooked many of the articles explicitly concerned with Jews. The number of relevant edicts presented in this essay is therefore more than twice that of previous compilations. This extensive material is systematically compiled in groupings: toleration, acknowledgement and legal protection for Jews; efforts at conversion, Christian-Jewish intermarriages, children and slaves of Jews; prevention of proselytising and the apostasy of converts; theological disavowal, rights limitation and suppression of the Jews. In conclusion, the significance of the Decretum Gratiani for the treatment of Jews is examined in comparison with other canonistic collections of the High Middle Ages, and is found to be relatively moderate. The appended tables not only provide a systematic overview of the relevant articles, but also list their origin, and their appearance in the more important pre-Gratian canonical collections.