The doctrine of the functions of law is an important component of the theory of law with significant cognitive and practical potential. However, the development of the doctrine of the functions of law not only occurs within the framework of the general theory of law, but is also formed through scientific achievements in individual branches of law. Nowadays, general theoretical sources distinguish more than twenty functions of legal impact on various grounds of classification. One of the methodological approaches to the systematization of the functions of law, which is necessary due to the increase in their number, is the division into core (actually legal) functions, which include regulatory and protective functions, and non-core functions, which include, in particular, compensatory, restorative, and restrictive functions. The purpose of the paper is to reveal those methodological features of the doctrine of the functions of labour law, which deserve the most attention in connection with their importance for its development in the context of contemporary challenges faced by labour law. The science of labour law has accumulated considerable experience of cognition of the functions of labour law. Changes in social life have created new problems, including in the field of labour relations: the phenomenon of unemployment, shadow employment, disparities in wages, continuing violations of the terms of labour contracts, poverty of working people, attempts by the state to “decline” its social obligations, significant labour migration, and many others. In the paper, the authors determined three reasons (factors) for the institutionalization of the doctrine of the functions of labour law: an increase in the level of cognition of law in general and labour law in particular, the presence of an ideological attitude to the active intervention of law in social relations, a certain level of humanization of the legal regulation of labour relations. The following methodological rules of cognition and formulation of functions have been defined: the rule of constitutional unity, the rule of the main direction, the rule of the purpose validity of individual functions, the rule of the direct inextricable connection of functions with each other. The paper concludes that the increase in the number of functions, named in different ways in the special literature, can be considered a perspective of the transformation into the quality of cognition of their essence, provided that the above-mentioned methodological approach is followed.