ABSTRACT: The UNCITRAL Working Group III is analysing possible reforms of the arbitral rules to address the risks associated with the increased prevalence of third-party funded (TPF) investment arbitration claims. TPF proponents claim that it provides access to justice for impecunious parties. Given the structural deficits in international investment law and claims are fulfilled from taxpayers’ funds, allowing unregulated TPF risks creating unjustifiable wealth transfers from the citizens of target states for the benefit of speculators. The research sets off with identifying the concerns associated with TPF in investment arbitration and follows with an exemplification of the available jurisprudence, specifically the Teinver v. Argentina arbitral award and the decision on Argentina’s annulment application, to understand the manner in which arbitral tribunals address the presence and impact of the funding agreement on the arbitration. Few jurisdictions, however, have legislated upon issues and concerns related to the TPF that could impact the arbitration. Within the UK and India there is a mix of traditional doctrinal principles, institutional rules and code of conduct to regulate claim-funding. This research paper attempts to trace the presence and concerns related to TPF in the ISDS system and also suggest few areas for law reform to prevent the adverse effects of TPF on developing states and on the investment law regime itself.