In light of the phenomenon known as government by contract, States and state entities often outsource the rendering of public services to private agents. This has led to a rise in the number of disputes, particularly arbitrations, between private and public parties. Against the background of a comparison between the English and Brazilian legal systems, this article argues that both procedural and substantive mechanisms are warranted to adequately safeguard the public interest which is implicated in such disputes. This article further explores the procedural and substantive mechanisms which have been implemented under English and Brazilian law, to find that Brazilian law has implemented procedural mechanisms which are more progressive than those provided under English law in terms of protecting the public interest. Nonetheless, this article concludes that both jurisdictions could improve their procedural and substantive frameworks applicable to arbitration proceedings involving public entities in order to achieve a more comprehensive protection of public interest