Sufism has been one of the most widely debated and contested fields within the Islamic tradition. Despite being a mainstay of Islamic religious life, it has been the subject of Muslim critical discussions for centuries. This has particularly been the case during the modern period. Indeed, over the past two centuries, many Islamic reformers and reformist movements have construed Sufism as the primary obstacle to the realization of piety and progress in Muslim societies. In this paper, I examine the relationship between the critique and defense of Sufism and the historical foundations of one of the most influential Islamic reformist movements in history, the Muslim Brotherhood of Egypt. An activist movement founded in 1928 by Hasan al-Banna (d. 1949), the Brotherhood is today understood to be a sharp critic of Sufism. However, as I show in this paper, during its earliest years, the Brotherhood positioned itself as an ardent defender of Sufism. Although the secondary scholarship on the Brotherhood has recognized the influence of Sufism on its organizational structure and educational program, the Brotherhood’s early defenses of the Sufi tradition have not been sufficiently examined. In this paper I analyze the Brotherhood’s earliest publicly facing writings on Sufism, which were printed in its early magazine, Jaridat al-Ikhwan al-Muslimin, to do two things. First, I uncover al-Banna and his Brotherhood colleagues’ deep commitment to Sufi esoteric and cosmological ideals. At the root of this commitment, I show, was their conviction in the primacy of the unseen spiritual reality. Brotherhood writers attributed the maintenance of this reality to the Sufi tradition and thus mounted a defense of that tradition in the face of growing reformist critiques. Second, I show that these Sufi ideals fundamentally informed al-Banna’s vision of the Brotherhood’s activist spirituality. As he depicted it, the Brotherhood’s mission was to confront a spiritually vacant Egyptian society and re-infuse it with a robust spirituality, the outlines of which he drew from Sufism. As such, Sufi esoteric and cosmological ideals, I argue, were far more essential to the Brotherhood’s activist approach toward Islam than previously understood. Most importantly, by highlighting this, my paper brings out the very significant role Brotherhood leaders and writers attributed to God as an agent and interlocutor in the realization of their activist project.