This article seeks to provide a comparative and up-to-date overview of the applicable rules and relevant practice of the European Court of Human Rights and of the United Nations Human Rights Committee on forum duplication in international human rights litigation. While specific inadmissibility clauses have been included in both the European Convention on Human Rights and the Optional Protocol to the International Covenant on Civil and Political Rights with a view to preventing multiple human rights petitions in relation to the same matter, their respective scopes differ. Moreover, the applicable normative framework has led to important—and diverging—judicial developments in Strasbourg and in Geneva, which may be of great significance in human rights practice and therefore deserve to be thoroughly addressed.