Legal systems have been originated in some sources and on the strength of these sources they establish civil law. All branches of law, more or less, have been compiled from similar sources but they are different in the degree of importance.In Common Diplomatic Law, General International Law and customs are at the first place then there are treaties, rules, judicial policies and opinion of jurists. Moslem jurists, though, different about sources of Islamic Law in general and sources of diplomatic law in Islam in special, count on Quran, Prophet’s Tradition and Consensus and Reason or Induction as the most important and prominent sources of Islamic Law. With a negligible regard, Common Law (orf), decrees and treaties can be counted as sources of Islamic law as well.In this paper, based on documentary method and content analysis, by applying library research, we are going to review sources of Islamic Diplomatic Law, i.e. Quran, Tradition, Consensus, Reason or Induction, Common Law and decrees.