In the legal system, understanding and identifying jurisdiction is critically important before the judicial mechanism gets into motion. It ensures that cases are heard in appropriate courts, where both parties have a fair opportunity to present their arguments and evidence. It prevents one party from unfairly gaining an advantage by choosing a court that may be biased or less favourable to the other party. Jurisdictional rules also help streamline legal proceedings by directing cases to the most appropriate courts. This avoids unnecessary delays and expenses associated with litigating in multiple jurisdictions or courts with limited authority. Jurisdiction determines which court's judgments are enforceable. Without proper jurisdiction, a court's decision may not be recognized or enforced in other jurisdictions, undermining the effectiveness of the legal system. The word ‘complementarity’ means the quality of being different but useful when combined.2 This paper will discuss the Complementarity principle in its application in Democratic Republic of Congo and International Criminal Court (ICC). This paper will also analyse the functioning of Military Court of Congo and complementarity with ICC and issues and challenges involved in Military Court of Congo and Complementarity principle Concern.