The principle of non-refoulement constitutes a fundamental protection for refugees. Concerning its concept, minimum protection for refugees is to secure their entry into states where they are given refuge from the real risk of being persecuted. This principle is clearly embedded in Article 33 of the 1951 Convention relating to the Status of Refugees. The restriction of refoulement, however, is only eligible for refugees who have been guaranteed their status as refugees by competent authorities. Due to the strict states' policy, the Convention does not cover certain individuals who have reasonable grounds for fearing to return to their countries. This gap was reflected by the UNHCR which defined such individuals as non-Convention refugees. This article examines complementary protection from the various multilateral or regional human rights treaties which have provided protection from refoulement for individuals falling outside the scope of the 1951 Convention. The main object of this article is to draw comprehensive grasp of non-refoulement outside the 1951 Convention by various approaches under international human rights law. As to protection for the non-Convention refugees, Part Ⅱ of this article explores the basic concept of complementary protection. Part Ⅱ also explains why the 1951 Convention needs to be complemented by other instruments. It criticizes feasibility of the 1951 Convention and ultra vires practices of states which hold their strict policy toward refugees and abuse the exceptional clause of non-refoulement. Part Ⅲ examines four complementary norms which provide their own non-refoulement. It compares Art. 33 of the 1951 Convention with 1) Convention against Torture, 2) International Covenant on Civil and Political Rights and 3) European Convention on Human Rights. Despite the common element, their jurisdiction, scope, level of protection varies significantly. This comparative analysis clarifies differences between the 1951 Convention and complementary protection and contains significant cases applied to non-Convention refugees by each complementary norm.