The article is dedicated to the history of interaction between the law of Muslims, subjects of Aragonese Kings, and Crown law in the 12—14th cc. The author shows that Islamic law is not rejected by the legal system of Christians. Sharia presented as a natural part within the hierarchical legal space of Kingdom.The author finds two different stages in the process of interaction; she bases her conclusions of the study of capitulations and royal privileges and emphasizes the aspect of judicial practice in the Muslim communities of the Kingdom. The results make it possible to determine the main principles and forms of the dialogue between Crown and Islamic laws at the time.