Founded in the mid-nineteenth century in London as a Christian organization committed to helping young men develop a healthy “body, mind, and spirit,” the Young Men’s Christian Association (YMCA) quickly evolved into a transnational organization with branches around the world. During the early twentieth century, the YMCA opened branches in urban centers throughout the Middle East, such as Istanbul, Cairo, Jerusalem, and Alexandria. This paper focuses on the formation and expansion of the YMCA after the First World War in Istanbul. Specifically, it examines how the signing of the Armistice in 1918, which brought an end to the war and the Allied occupation of the capital, radically reconfigured the social, political, and cultural landscape in which the YMCA and other voluntary associations operated. According to an Armenian member of the YMCA in Istanbul in the early 1920s, “by the signing of the Armistice a new life came into the Association. New men began to come in bringing with them fresh power and enthusiasm. Members began to flock in again and the work was on a fresh start.” Prior to the war, the YMCA focused its energies on providing its members with Bible classes, concerts, excursions, and reading activities. After 1918, it embraced a more public role, by expanding its activities beyond reading and discussing religion, to include a diverse array of educational, social, and physical activities. This paper examines the relationship between the sociopolitical landscape of the period and the institutional and discursive shifts of the YMCA in Istanbul. Drawing from a diverse array of multilingual unpublished reports, surveys, newspapers, and vernacular photographs, this paper argues that the institutionalization and expansion of the YMCA during the armistice offers unique insights into the period, the city, and the formation of the organization as a transnational brotherhood. The argument advanced is part of a broader book project project, which examines the transition from empire to nation-state through the lens of the YMCA.