This essay provides a comprehensive analysis of the principle of complementary jurisdiction as exercised by the International Criminal Court (ICC). It begins by defining the concept and tracing its origins to the International Criminal Tribunal for the former Yugoslavia (ICTY) and the International Criminal Tribunal for Rwanda (ICTR), highlighting the shift from 'concurrent jurisdiction' to the 'complementary jurisdiction' model established by the Rome Statute. The essay focuses on Article 17 of the Rome Statute, which outlines the conditions under which the ICC can intervene, emphasizing the primary role of states in prosecuting international crimes. It explores the tensions that can arise between state parties and the ICC, using the Libyan cases (Gaddafi and Al Senussi) as examples. The essay critically discusses the jurisprudence, evaluating whether complementary jurisdiction upholds or challenges state sovereignty. The essay also examines the ICC's jurisdiction, including the four core international crimes (genocide, crimes against humanity, war crimes, and crimes of aggression), and the conditions under which the ICC can initiate investigations, including referrals from states, the UN Security Council, or the Prosecutor's own initiative. The essay concludes by emphasizing the importance of cooperation between the ICC and domestic courts to ensure justice and maintain peace.