Human right is a topical issue globally but attaining it has remained very difficult. Every day, people around the world face different forms of dehumanizing treatment from their governments, multinationals and other groups. For decade too, strong institutions have emerged to fight for the rights of the voiceless and the weak. One of these institutions is Amnesty International (AI). This paper examines the activities of Amnesty International in the promotion and protection of human rights vis-a-vis the nature of operations, contributions and challenges in Nigeria. The paper adopts desk research design, which is based on secondary sources from journals, books and other printed materials. Findings revealed that AI has significantly contributed to the promotion of human rights in Nigeria through different approaches such as advocacy/campaign, governance peer review, shaming-and-naming approach, and support for domestic civil rights groups, among others. However, findings also showed that the main challenges of AI are the negative perceptions of some sections toward the organization as a tool for promoting western ideology and the low awareness and involvement of individuals at the grassroots in developing nations like Nigeria. The paper recommends that the organization intensifies its promotional activities in a manner that would improve its reputation as well as help to educate and provide access for engagement of locals in developing countries.