The article discusses the legal content of the principle of efficiency of public expenses in Russia as one of the underpinnings of the financial activities of state and municipal entities in Russia. The author analyzes the current legislation, identifies the characteristics of the principle of efficiency of public expenditure in certain legal norms. The author finds that the principle of effectiveness of public expenses is incompletely regulated in Russia. The article concludes that the principle of effectiveness of public expenses is the institutional principle of financial law. The principle of effectiveness of public expenses covers all financial activity of state and municipal entities associated with the expenditure of public funds.