Many studies have been conducted on various topics of the application of Islamic law in Indonesia, Malaysia, and Brunei. However, we believe very few have tried to see the similarities and differences in the application of Islamic law, the law that forms the basis of the way of life of Muslims in the three allied countries. In order to understand the problem and application of sharia law from the point of view of similarities and differences between the three Malay countries, we have conducted a series of data analyses of the sharia law literature in the three Malay family countries. Meanwhile, to answer this research question, in the process of gaining understanding, we conducted a study using a phenomenological approach, a study technique to gain an understanding of something phenomenal among the existing data. Among other things, we coded the data, critically evaluated it, and interpreted it to obtain the relevance of the application of Islamic sharia in three Malay lands that both share Islam. Secondary data fully support this research; in the form of scientific evidence that we extracted from various published literature, both in the form of books and scientific journals, provided that we get valid answers to research problems. After examining it in depth, we can conclude that there are similarities between the three allied countries that have implemented their laws based on Islamic law. However, their application is still limited, and the difference is that Indonesia is a country based on Pancasila while Malaysia is based on Islamic law. Brunei Darussalam is entirely based on sharia law. Regarding criminal law, Indonesia still uses positive legal sources, while civil law, which covers marriage and inheritance, fully adheres to sharia law. Thus, these findings become essential inputs for the development of future studies