This chapter discusses the role of expert witnesses in international arbitration, as well as the responsibilities of that role. The roles, functions, and ethical obligations of expert witnesses are still tentatively defined within the realm of international arbitration, but there have been some important regulations and procedures imposed already — the International Bar Association (IBA) Rules of Evidence, for example. This is a significant attempt in regulating the conduct of experts, as well as in laying down the distinctions between party-selected and party-anointed experts, among other innovations. But of course, the legal system employed within the sphere of international arbitration will continue to change in response to unforeseen flaws in entrenched practice — as will be the case for expert witnessing. Perhaps, in order to address one of the possible abuses of the latter, ethical reforms might also be applied to the structure of roles in the courtroom.