In this paper, I draw on historical and ethnographic research to trace the history of Muslim-Christian encounters in colonial Mali. At the dawn of French colonialism, Muslims were a minority among colonial subjects in what is present-day Mali, and Muslim missionaries flourished in the wake of the so-called colonial peace, successfully Islamizing many of their fellow colonial subjects. In fact, one of the unintended consequences of colonial rule was mass Islamization. Entering this dynamic scene, the Roman Catholic missionary order, the Missionaires d’Afrique or White Fathers, attempted with little success to bring Catholicism to Muslims and non-Muslims—glossed as “animists” by missionaries and the colonial administration. Drawing on written and archival sources as well as ethnography, the paper focuses on the White Fathers’ mission activities in which the attempt to thwart the spread of Islam was sometimes an explicitly stated objective. It shows how contentious Muslim-Christian encounters, which have echoes in oral history, the contemporary social imaginary, and every practice, reverberated over the following decades where such encounters have often been fraught with tensions. Though Christians remain a small minority in Mali, the tensions surrounding their history have left traces, though sometimes difficult to excavate.