The article examines the adversarial principle, its legislative consolidation. This paper analyses the concept of the adversarial principle as the primary principle of the civil procedure. The case law of the European Court of Human Rights on the adversarial principle is examined. The article analyzes the opinion of such scientists as Komarov, Stefan and Mamnitsky. The article highlights elements of the adversarial principle. There are: 1) right of the parties to participate in the process; 2) the right to justify claims and objections; 3) the right to petition; 4) the right and obligation to adduce evidence; 5) the right to submit new and additional materials in the court of appeal, cassation, etc. Ability in litigation requires that the prosecution, defense, civil claimant and defendant have the same opportunity to convince the court of their correctness. The parties and other parties involved in the case have equal rights to adduce evidence, to investigate and to prove their conviction. The court has a leading role in the trial it facilitates the full, comprehensive clarification of the circumstances of the case and adjudicates on the basis of internal conviction, guided by law. This principle is undoubtedly a historically conditioned legal phenomenon, since, at a particular stage of society's development, depending on national peculiarities and legal traditions. This paper analyses the legislative consolidation of the principle of competition in the Constitution of Ukraine and the Civil Procedure Code of Ukraine. Moreover, the article explores the practice of the European Court of Human Rights. Such as Garcia Ruiz v. Spain case, Montovanelli v. France case, Salov v. Ukraine case and the case of Lazarenko and Others v. Ukraine.