In Investor-State Dispute Settlement (ISDS), ‘double hatting’, or the playing of multiple roles by arbitrators in different ISDS proceedings as counsels, expert witnesses, or tribunal secretaries, is a problematic phenomenon. This deplorable practice results in the monopolization of power and builds up suspicions regarding such arbitrators’ impartiality which, in turn, threatens the legitimacy of the whole ISDS regime itself. Therefore, to sustain the current ISDS system as a viable dispute resolution option for investors and states, there is a need to regulate double hatting at the earliest. To that end, numerous solutions to this problem have been forwarded by scholars and international bodies alike. The recently proposed Draft Code of Conduct for Adjudicators in ISDS is a significant development in this field. However, all of these solutions are either unviable or inadequate as they fail to account for the variations in the forms and intensities of double hatting. To remedy this lacuna, this article analyses the existing proposals, including the Draft Code of Conduct, and, thereafter, develops a more comprehensive solution by inculcating measures such as compulsory disclosure requirements and temporal bans. Further, it adapts these measures to regulate, and minimize, concurrent and successive double hatting across different classes of arbitral proceedings. By doing so, this article adopts a novel, multi-faceted approach to overcome the problem on a case-by-case basis, serving its aim of bringing to the table a viable and effective solution—one that ticks the maximum boxes—to resolve the menace of double hatting.