This article compares Indonesian legal system and Malaysian legal system. The government legalized Islamic law in national legislateions, which are in effect for Muslim people. To facilitate dispute settlement, there is a religious court to solve Islamic dispute based on Islamic Law. The exsistence of Islamic law in Indonesia and Malaysia has similarity and differentiation. The similarities among others are: the Muslim-majority in both countries pushes the government to put Islamic law into force, Islamic law must be written into constitution or legislation. It is needed to have legal basis when performing Islamic law, the existence of religious court is very important in dispute settlement related to Islamic law. The Influence of western legal system is very strong in national legal system. Nevertheless, the western legal system differ substantially from Islamic legal system, and Islamic law was implemented limitedly based upon western legislation. It was limited to family law. While the differentiation are: the way of implementation of western legal system into national legal system and the form of legislation Indonesia has one legislation, which is in effect to all of Indonesian people. On the contrary, Malaysia has many enactments, which are different from one to another in each negeri.