The Greek anti-Ottoman revolt in the 1820s brought increased suspicion among the empire’s ruling circles toward not only Greeks but non-Muslim subjects in general. This sparked government security measures in Istanbul, home to substantial Christian and Jewish populations. This article examines such measures intended to bring non-Muslim subjects under control, and the overall impact the Greek revolt had on the Ottoman approach to its subjects. It argues that the revolt catalyzed changes in the state’s attitude toward population surveillance and its treatment of non-Muslims. When the empire felt the need to bring non-Muslims under control, a major challenge was how to verify and vouch for the latter’s identity, since they deemed Muslim officials incapable of doing so. Thus, though they were suspicious of non-Muslims, they actively used the religious authorities of their communities to implement various security measures, including the creation of a population record and the introduction of internal passports. At the same time, religious authorities found it essential to demonstrate their and their community’s pro-Ottoman position by cooperating with the state in its efforts to find enemies within. Incorporation of non-Muslim religious authorities into imperial governance led to official recognition of the representatives of smaller non-Muslim groups, including Latin subjects, Armenian Catholics, and Jews. The result was a standardization of non-Muslim communities with officially recognized representatives before the government.