After Bulgaria's accession to the European Union, the global business environment was subject to some changes related to the process of globalization, the dynamic development of markets, and the free movement of people within the community. These changes required that Bulgarian tourism enterprises seek new opportunities for gaining a competitive advantage based on the quality of their products and tourist services. This issue requires an investigation into the economic implications considering the single EU market and the associated challenges to the competitiveness of Bulgarian tourism enterprises. In order to obtain certificates for globally or nationally recognized quality marks and signs, tourism enterprises have to reorganize their activities in such a way as to meet the requirements for obtaining such certificates and the associated registered marks, which requires investment of time and money, as well as certain managerial skills. An alternative to this type of quality assurance of the tourist services is the development, implementation and certification of a Quality Management System (QMS) in accordance with the provisions of the ISO 9001 standard. This standard allows tourist enterprises to build quality management systems that are consistent with the specifics of their business and service technologies and processes. The aim of this article is to define the benefits for a tourism enterprise from the implementation of a QMS and certification under ISO 9001 to ensure the quality of their tourist services. To this end, the article reviews the available studies related to the quality assurance in the tourism sector in Bulgaria and the degree of its compliance with the ISO 9001 standard. The study demonstrates the author's thesis that the use of the most widely used international standard gives the tourist business the opportunity to demonstrate its ability to manage quality, irrespective of the category of the tourist site and the developed tourism activity, using a clearly identifiable and globally recognised quality sign.