Abstract: This article discusses on the definition of subsidiary legislation in Malaysian administrative law, its advantages and how to challenge it. Subsidiary legislation is part of Malaysian legal sources that supplements the legislative function of Malaysian legal system. Although the Parliament and State Assembly are the main bodies that have been vested with the legislative power in Malaysia, other non-elected members are also conferred to exercise the same function to assist the Parliament and the State Assembly in their law making roles. The abundance of subsidiary legislation in the legal systems serve a great deal of benefits and advantages especially to ease the burden of the legislative bodies especially in dealing with the details of the law and also to gain expert views on certain issues. However the power mandated in the hands of these authorised bodies comprising of non-elected civil servants could also result in illegality and abuse of power, thus, this article attempts to outline grounds on which the subsidiary legislation can be challenged.