In 1681, a large group of Muslim residents from the Kemer Hatun neighborhood of Istanbul—including the imam Mustafa Efendi—came to court. They collectively stated that an Armenian resident of the neighborhood named Serkiz had built a church in a residential area that included in its interior candles (kandil), trump (sûr), and fire (isnam). In addition, Armenians were performing their “superstitious rituals and prayers” (ayin-i küfri) there, which were led by several priests, namely Andon, Andos, and Serkiz. They mentioned that while the Armenian community of the church had previously been prohibited from performing these rituals by a ruling of the court, they were still engaging in them with the participation of even more men and women than before. In addition to performing their rituals, the attendees were congregating around the church to drink wine and engage in similar “misconduct.” For these reasons, the plaintiffs demanded the church’s demolition and the court assigned several officials to investigate the situation. Ultimately, by citing the principle that it was not permitted to build [new] churches in the lands of Islam (Bilad-i İslamiye) according to Islamic jurisprudence, the court once again prohibited the community from using the building as a church. By utilizing unpublished legal court records as well as registers of important affairs (mühimme defterleri) and registers of complaints (şikayet defterleri), this paper examines churches and the central role they played in intercommunal relations in Istanbul during the second half of the seventeenth century, with a specific emphasis on the district of Galata and its ethnically and religiously diverse population. Amid heightened religiosity in the seventeenth century, space served as a medium through which communal interests were advanced and communal differences were enacted. By competing for control over space and strengthening the spatial boundaries of their communities, the religious and ethnic communities of Istanbul aimed at forming distinct identities based on intracommunal bonds. Christian churches were crucial components of this spatial competition and received unprecedented official and public attention during this period. This paper seeks to focus on two neglected issues regarding the regulation and treatment of churches in Istanbul: 1) how the reactions of non-Muslim communities to this regulation, including their use of residential spaces as sacred spaces, cemented their intracommunal solidarities, and 2) how contested sacred spaces were crucial to the process of redefining sociocultural hierarchies within the Ottoman system during this period and in subsequent centuries.