In the history of Christian-Muslim relations, the rise of Islam and its encounter with Christianity is often characterized as the competition between two missionary religions, but this is a narrative formed by Western Christianity’s engagement with Islam long after Islam’s formation. It represents an anachronistic understanding of how Christians and Muslims viewed and related to one another in the formational period of Islam. In particular, it neglects the history of Syriac Christians who lived amidst Muslims in the first centuries of Islam’s existence, and therefore a significant part of the earliest engagement between Muslims and Christians has effectively been a lost history. When works on Islam recognize the presence of Syriac Christians (Eastern, non-Chalcedonian Christians), it is generally confined to two areas: their work in translating philosophical and scientific texts into Arabic during the golden age of Islam, and their status as ahl al-dhimmah (protected people). There remains a gap in our understanding of the relationship they had with one another and how this may have shaped each religion’s self-understanding as they navigated a new form of religious pluralism. This study examines the Church of the East and its relation to Islam in the 7th to 9th centuries CE. This will help flesh out our understanding of Christianity’s early relationship to Islam through the lens of the Church of the East with the hope that it may help inform relational possibilities between followers of these religions today.