The author looks at the ‘inherent powers’ of the WTO Appellate Body (AB) and ICSID tribunals. She argues that the key to the exercise of the international judicial function is the principle of inherent powers, which are conferred upon judicial bodies to safeguard the judicial function. Yet, for the WTO Appellate Body and ICSID tribunals , it is often assumed that while ICSID tribunals have broad inherent powers, the AB’s inherent powers are restricted. She asks the question whether this means that these tribunals are fragmented in the exercise of their judicial function, and consequently their inherent powers, and if so, what factors contribute to such fragmentation. This chapter answers the above questions by examining the way the AB and ICSID tribunals perceive their authority to exercise inherent powers through the examples of objections to admissibility of a case and amicus curiae submissions. Using these examples, this chapter challenges absolutist assumptions about the inherent powers of the AB and ICSID tribunals. Instead, it develops a nuanced understanding of the scope of the inherent powers of these tribunals through a study of their respective judicial functions.