Abstract The Central American Court of Justice (CACJ) (1907-1918) was created with the goal of minimizing conflict between the five republics: El Salvador, Costa Rica, Guatemala, Nicaragua, and Honduras. The CACJ, however, has attracted scant scholarly attention. Nonetheless, the Court is academically significant and historically relevant. The CACJ was not only the world’s first supranational body to which states would suspend their sovereignty and submit all complaints, but also evidence that international organizations could facilitate state cooperation and create peace. Addressing the gap in the literature through extensive archival research, this study finds the following. First, the Court played an instrumental role in mediating regional peace and averting war between the republics. Second, it addressed controversial issues concerning state relations such as non-intervention, the law of the sea, and international treaty obligations. Third, due to the Court’s profound legal work, it still continues to have the potential to contribute to international law and institutions. Finally, although Washington played a significant role in the Court’s rise and demise, the Court demonstrates the ability of Latin American countries to address their own regional issues. As a result, the CACJ is a valuable underexplored subject that merits historical consideration.