Customary institutions are key for understanding patterns of pastoralist violence in Africa. Previous research has demonstrated a strong link between customary institutions and peace, yet the specific institutional functions influencing pastoralist violence remain poorly understood. I address this gap by proposing that effective governance – whether formal or customary – depends on three essential functions related to the creation, enforcement, and adjudication of rules. Drawing on unique field-collected data from Madagascar, I examine how formalized customary institutions, locally known as ‘dina’, shape regional variations in violence across two regions in southern Madagascar. This area has witnessed an unprecedented surge in pastoralist violence over the past decade, driven by violent cattle raids carried out by organized criminal groups known as ‘dahalo’. Amidst this turmoil, some regions have remained relatively peaceful, and in this article, I explore whether differences in customary institutional traits can explain regional variations in pastoralist violence. My analysis reveals that a high degree of community involvement in rule making, combined with an efficient enforcement mechanism, is essential for effectively mitigating pastoralist violence. Furthermore, a just and impartial adjudication process fosters greater institutional trust, which also contributes to reducing violence. These findings carry significant policy implications, highlighting the specific characteristics of formalized customary institutions that are critical for addressing the rapidly escalating violence associated with cattle raiding in Africa.