This chapter explores in considerable detail differences and similarities between the Islamic legal tradition and international law. It discusses in detail the historical interaction between these legal traditions, their co-evolution, and the academic conversations on this topic. The chapter also addresses the Islamic milieu’s contributions to international law, and sources of Islamic law including the Quran, sunna, judicial consensus, and analogical reasoning. It talks about the role of religion in international law. Mapping the specific characteristics of Islamic law and international law offers a glimpse of the contrasting and similar paradigms, spirit, and operation of law. This chapter identifies three points of convergence: law of scholars, customary law, and rule of law; as well as three points of departure: relation between law and religion, sources of law, and religious features in the courtroom (religious affiliation and gender of judges, holy oaths).