The subject of this paper is a type of letter of credit that is not commonly encountered in the practices of domestic banks. It is not specifically regulated by domestic legislation; however, its significance is expected to grow in the international business relations of our businessmen with companies from other countries where the use of this payment security instrument is common in the banking industry. This type of letter of credit is theoretically of disputed legal nature, raising questions about whether it qualifies as a letter of credit, a type of guarantee, or a distinct legal institute. The focus of the research is on the standby letter of credit as a security measure in international contractual relations, particularly in sales and construction contracts. In sales contracts, the standby letter of credit serves to secure the interests of the seller, while in construction contracts, it can secure interests of both the client the contractor, depending on the party for whose benefit it was issued. The paper aims to define the standby letter of credit, explain its role in protecting the rights and interests of contracting parties, and explore its legal nature. In particular, we will conduct a comparative analysis between this legal institute and a 'classic' documentary letter of credit and a bank guarantee. In our legal theory, and to a greater extent in American and English legal theory, there are numerous works that deal with the topic of standby letters of credit. However, the legal regulations related to banking operations have changed over time, which requires a fresh perspective. The goal of this work is to familiarize our companies and banks engaged in transactions with foreign entities, where the issuance of this type of letter of credit is customary, with the role of a standby letter of credit as an instrument for ensuring contractual obligations. In addition to that, the paper aims to explore the legal relationships established with this type of letter of credit.