The article considers property of axiomaticity, property of presumptiveness and property of dogmatic fictitiousness of the constitutional principle of good faith of subjects of legal relations. Structural systemic analysis, comparative legal analysis, method of formal logic and other methods have made it possible to identify and characterize these properties. Using combination of these methods, this researcher was able to address not only the issues of constitutional law of current importance, but also issues pertaining to law theory, as well as other branches of law. The purpose of the research is to test the hypothesis that, in a global sense, good faith is the foundation upon which the entire legal system of a state is built. The constitutional principle of good faith of subjects of legal relations formulates the basic rule which is that «good faith is a prerequisite for the activity of subjects of legal relations». In this regard, the principle is axiomatic and determines the direction of the further development of the legal system within the framework of the formulated rule. Also, the constitutional principle of good faith of subjects of legal relations, obliging the law practitioners to proceed on the assumption of good faith of subjects of legal relations that duly observe the Constitution of the Russian Federation and the legislation, assumes a property of presumptiveness and thus ensures the stability of the state’s legal system. Presumption of good faith of the subjects of legal relations, while providing for the possibility of rebutting such an assumption, is an instrument for monitoring compliance with the criteria of good faith formulated by normative legal acts by the subjects of a particular branch of legal relations. In turn, the principle of good faith of subjects of legal relations due to the high degree of legal generality and the absence of clear boundaries of its legal meanings has the property of dogmatic fictitiousness, which allows to fully disclose its provisions, thus developing the legal system and ensuring its effective functioning. Thus, these properties allow the principle of good faith of subjects of legal relations to fully realize its potential and to carry out further full development, as well as the normative consolidation of aspects of good faith in various branches of law.