This article is dedicated to a comprehensive analysis of the procedural and legal significance of the institute of preliminary securing of testimony in criminal justice. The research substantiates that the key objective of this institute is to ensure the reliability, immutability, and admissibility of testimony in conditions where there is a threat of evidence loss (e.g., serious illness of a witness, their prolonged departure, or other objective reasons). The article thoroughly examines the procedural grounds, competent subjects, procedure for preliminary securing of testimony, as well as the legal force of the obtained evidence in subsequent judicial proceedings. The role of this institute in ensuring the principle of adversariality of the parties is separately considered, including guarantees for the participation of the defense and prosecution in the evidence securing procedure. The conclusions present scientific and practical recommendations for further enhancing the significance of this procedural tool for achieving fair justice and establishing the truth.