The increasing recognition of amicus submissions in international arbitration has sparked a lively debate surrounding their admissibility and the potential impact on the core principles of International Arbitration. This article delves into the various areas regarding the admissibility of amicus submissions within the context of Investor-State Dispute Settlement (“ISDS”), while also highlighting the significance of amicus submissions through references to seminal decisions of tribunals in various disputes. A global perspective on amicus submissions is provided, with a primary focus on the North American Free Trade Agreement (“NAFTA”) and the International Centre for Settlement of Investment Disputes (“ICSID”). The article explores the benefits and challenges associated with amicus submissions, delving into their potential to enhance transparency, incorporate diverse viewpoints, and provide valuable insights to tribunals. It also acknowledges the concerns raised by critics, such as the risk of introducing biases, the possibility of diluting the arbitration process, and the potential for amicus submissions to be used as a delaying tactic by parties. However, it is outweighed by authorities such as environmental and human rights NGOs or public authorities. To address these concerns, the article suggests criteria for determining whether amicus submissions should be permitted, emphasising the need for a balanced approach that considers the potential contributions of amicus submissions while also safeguarding the efficiency and fairness of the arbitration process. Furthermore, the article delves into the Indian ISDS regime, with a particular focus on the RAKIA dispute, to underscore how amicus submissions can play a crucial role in representing the voices of non-parties not only against the investors but the state as well. By allowing third-party perspectives to be heard, amicus submissions can contribute to a more equitable arbitration process, ensuring that broader public interests are considered and that the outcomes of ISDS cases reflect a more comprehensive understanding of the issues at stake.