The article analyzes the concept of good faith on the example of its development in civil proceedings in Germany and France. The author traces the relationship between the good faith of Roman civil procedure and the good faith of continental European countries, which was developed through the reception of Roman law. he author examines a number of sources of the so-called barbarian law in the context of good faith and its negative manifestation - bad faith in procedural communication and counteraction thereto. The author defines good faith as a condition for proper procedural behavior in the sources of law of the Holy Roman Empire of the Germanic nation and traces the history of the term Treu und Glauben. The author examines the concepts of correlation between the Roman term bona fides and the German term Treu und Glauben, which has become a general principle of various branches of law, including civil procedure law. The author examines the presence of the good faith principle in the modern German Code of Civil Procedure. The author also analyzes the concept of the formation of the principle of good faith in civil proceedings in France, for which purpose the medieval rules of customary law contained in such legal sources as the Coutumes Beauvais are studied. Special attention is paid to an important source of French procedural law of modern times - the Ordinance of Louis XIV of 1667 (Louis Code), which was the basis for the Civil Procedure Code of Napoleon of 1806 and whose provisions contained measures to counteract the abuse of procedural rights, and in some cases the term good faith as a measure of exemplary procedural communication. The author also reviews the provisions of the current French Code of Civil Procedure, which entered into force on January 1, 1976, where the principle of good faith is applied both as a counteraction to unfair procedural behavior and as a standard of procedural behavior which provides for the proper performance of duties and exercise of rights. The author determines that the principle of good faith is primarily found in substantive law, both in Germany and France, from where it is integrated into procedural law.