In the event of death, an appointment of a wasi is considered as an important requirement under the law because he plays a vital role in ensuring the deceased’s estate to be managed properly and efficiently. In addition, the appointment of wasi may expedite the process of administration and distribution of property and avoid disputes among the family members of the deceased. In Malaysia, the Rules of Court 2012 does not include the estate of a Muslim dying leaving a will because it does not come within the scope of the Wills Act 1959. However, the existence of will with the appointment of a wasi is valid for application of grant of Probate though the fact it is a Muslim will. Moreover, the appointment of a wasi is not clearly mentioned in any states’ enactment but it is only provided under the statutes of general application such as Probate and Administration Act 1959. Thus, this paper attempts to analyse the laws on the appointment of a wasi in estate administration. This study is based on a qualitative study and its approach is a content analysis methodology. This study reveals that the laws governing the appointment of a wasi in Malaysia involves a dual legal system and it subjects to several legal constraints under federal and state laws. The findings of the study provide room for further improvement with regards to the appointment of a wasi particularly in the administration of Muslim’s estate. The study concludes that there is a lacuna in the existing laws where the appointment of a wasi is not expressly clarified in any state laws except provided in federal laws.