It is argued that the organisations that are best suited to represent the interests of the affected people of the host state and advocate for the protection of human rights in investor-state arbitration are non-governmental organisations (NGOs). According to the authors, NGOs allow public interest considerations to be taken into account while the tribunal broadly looks at all the issues involved in the dispute. It is also argued that NGOs, by being permitted to participate in arbitral proceedings, ensure transparency, which is often regarded as one of the primary solutions to the negative reactions to investor-state arbitration. To that extent, this chapter will attempt to explore public interest litigation vis-à-vis amicus participation in investor-state arbitration. Notably, this chapter begins by examining why human rights are not assigned the desired importance in most investor-state treaties and agreements. The second section discusses why the ‘interests of the public’ in the host state need to be represented in investor-state arbitral proceedings. The third section delves into analysing the potential role that NGOs can play in representing ‘public interests’ and ‘human rights’ issues before the arbitral tribunals through recent case studies. The fourth section discusses the safeguards and measures that can be taken to address the criticisms that have been levelled against the permitting of amicus curiae interventions in investor-state arbitral proceedings.