In international arbitration there are few different competent bodies to hear challenges of arbitrators. Who will have the jurisdiction to rule on a challenge depends primarily on the parties’ wishes. Party autonomy is corollary of international arbitration and if parties in their arbitration agreement or subsequently during the course of the proceedings choose the appointing authority, the question of jurisdiction is solved. However, if that is not the case, a jurisdiction for challenges depends on the form of arbitration. In arbitration conducted under institutional arbitration rules, the prevailing competent body which rules on the challenge is an arbitral institution that administers arbitration or, more specifically, the appointing authority. There are two exceptions to this prevailing method in institutional arbitration. First is ICSID challenge procedure where the unchallenged arbitrators are authorized to decide on their co-arbitrators challenge. The second exception are the DIS Rules where the whole tribunal has the competence to decide on the challenge of an arbitrator. On the other side, in ad hoc arbitration there are also a few methods for decision-making on the challenge, but which all overlaps with previously mentioned. The first situation is when the parties, although their arbitration is not administered by some arbitral institution, choose the appointing authority to reach a decision in case of their disagreement about a certain issue, for example, the challenge of an arbitrator. Second, if the parties did not choose any method of resolving the challenge, then the provisions of lex arbitri are applicable.