The role of non-Muslim translators in the transfer of ancient Greek medical knowledge to the medieval Muslims, and thence to medieval Europeans, is well known. Yet the scholarly quest for “Islamic contributions to civilization” has contributed to underestimating the ongoing role of Jewish and Christian physicians, after the initial translation movement, in the professional practice of medicine of the medieval Middle East. Medical training and practice in the Middle East continued to cross religious boundaries throughout the medieval period. This paper uses three late medieval Arabic biographical dictionaries and narrative sources in Syriac, Arabic, and Armenian to demonstrate the full participation of non-Muslim physicians, into the late medieval period, in the often grudging collaborations which we term “Islamic” medicine. The biographical dictionaries used are the well-known works of Jamal al-Din al-Qifti and Ibn Abi Usaybi'a, as well as the unedited Rawdat al-alibba fi tarikh al-atibba of Daud b. Nasir al-Din al-Mawsili in the early fifteenth century. While much of al-Mawsili’s text was borrowed from Ibn Abi Usaybi'a’s work, he reordered and supplemented that earlier material in order to emphasize the importance of his native Jazira. In the process, he also revealed that into the fifteenth century, the medical profession drew from the various local religious communities. The biographical dictionaries will be supplemented by anecdotes culled from narrative sources, including the Syriac chronicles of Bar 'Ebroyo (Ibn al-'Ibri) and the travel account of Ibn Battuta. My paper builds on the research for Egypt by Jason Zaborowski, expanding to include a later period and a larger region in late medieval Anatolia, Jazira, and Iraq. Rather than presenting medicine as a secular meeting-ground for inter-religious convivencia outside of religious discourse, however, this paper argues that both Islam and Christianity linked healing to God. Rather than medicine being free of religion, it was a domain of shared goals among people of different religions. Religious practice was expected in medieval Middle Eastern medicine, and a plurality of religions continued to be attested among practitioners and teachers as well as among patients and pupils. The religious diversity of late medieval Middle Eastern medicine reveals non-Muslims as participating powerfully in “Islamic” society and culture, thus presenting an alternative to the common scholarly presumption that non-Muslim minorities were marginalized and of negligible historical importance in the late medieval period.