The subject of this research is the investigator's authority to apply the security measures provided for in the Federal Law “On State Protection of Victims, Witnesses, and Other Participants in Criminal Proceedings”. In particular, the article examines the reasons and grounds for applying security measures, the investigator's interaction with the authorities responsible for implementing these measures, and the procedure for storing the criminal procedural acts related to their application. It is shown that certain aspects of ensuring the safety of participants in criminal proceedings are regulated not only by the aforementioned Law but also by a number of provisions in the Criminal Procedure Code of the Russian Federation.