The object of this research is the legal relations emerging in the process of protection of the rights of an undetermined circle of people in a court by competent officials from the prosecutor’s office of the Russian Federation. The subject of this research is the sum of norms regulating prosecutorial participation in a civil proceeding for protection of rights of an undetermined circle of people, as well as theoretical and practical aspects of using legal means of the prosecutor in this sphere. It is determined that there are still instances in the process of prosecutorial participation in civil cases of erroneous interpretation of the “undetermined circle of people” by the subjects of law enforcement, which impedes the process of protection of the rights and freedoms of the undetermined circle of people by the Russian authorities. In the process of analyzing the rulings for 2019, the author outlines the qualifications for the undetermined circle of people, provides examples of improper interpretation of the concept of “undetermined circle of people” by the courts, and describes unequivocal typical statements of claim submitted by prosecutors in defense of undetermined circles of people, and cites mistakes made by authorized staff of the prosecutor’s office during filing.