An international non-governmental organization is a volunteered self-established non-profit organization which advocates public interests. The role of non-governmental organizations' which inherently persue public interests, are significant and have been recognized at different levels such as friend of the court (amicus curiae), plaintiff and plaintiff representative. Meanwhile, according to the European Convention of Human Rights and its protocols, especially Protocol No. 11, as well as the practice of the European Court of Human Rights, which is one of the main resource of the present study, the possibility of non-governmental organizations’ participation has been accepted in three forms: plaintiff, plaintiff representative and amicus curiae. This is why one can talk about the extensive role of international non-governmental organizations in the proceedings of the European Court of Human Rights. This study aims to examine this role.