Tourism is considered to be the leading generator of economic development in the world. For its growth it requires a clean and immaculate environment. The concept of sustainable tourism emerged as a possible solution to face that challenge. What sets sustainable tourism apart from other forms of tourism, in a special way, is how sustainable tourism encompasses ecological, economic and social aspects of sustainable development with the intention to establish a long-term balance of these three dimensions. With the aim to increase the long-term economic benefits from tourism, it is required to embrace and implement an adequate tourism development strategy focused on sustainable development and the increasing quality of tourist services in the tourist destinations. In a dynamic market conditions, hotel companies have to adapt their offer according to the tourist demand and provide a high-quality service that meets or exceeds tourists` expectations. In order to accomplish this goal, it is important to implement a quality management system (QMS) in hotel companies. This doctoral dissertation investigates the implementation of the quality management system (QMS) and Sustainable Development (SD) principles and their impact on the economical, environmental and social aspects within the context of hospitality. The investigation sheds light on how the adoption of QMS and SD principles can lead to enhanced economic outcomes. These outcomes manifest through increased operational efficiency, cost reduction, revenue growth, contributing to the overall financial sustainability of the hotel business. The environmental impacts of the implementation of QMS and SD principles in hospitality highlights how waste reduction, energy conservation, sustainable sourcing, and eco-friendly practices can not only reduce the ecological footprint of businesses but also enhance their reputation as environmentally responsible hotels. The social dimension reveals how the implementation of QMS and SD principles positively affect work conditions, employee satisfaction, employee motivation and donations. By aligning economic, environmental, and social objectives, hotel companies can achieve sustainable competitive advantage, enhance their long-term viability, and contribute positively to society. When defining the hypotheses, domestic and foreign literature was extensively reviewed. All basic constructs are elaborated in accordance with theoretical background. The hypotheses are the following: „The implementation of the quality management system principles and the principles of sustainable development have a statistically significant impact on the economic, environmental and social aspects of hotel business performance“  H1: the implementation of the quality management system principles and the principles of sustainable development have a statistically significant impact on the economic aspects of hotel business performance  H2: the implementation of the quality management system principles and the principles of sustainable development have a statistically significant impact on the environmental aspects of hotel business performance  H3: the implementation of the quality management system principles and the principles of sustainable development have a statistically significant impact on the social aspects of hotel business performance. A survey method using a structured questionnaire is applied in which all questions are mandatory. The respondents were managers (CEO, General managers and/or their deputies or assistants) of large and medium-sized hotel companies in the Republic of Croatia. The required minimum sample size was calculated using GPower software, which calculated that the minimum acceptable sample size is 118 respondents. The total number of collected questionnaires was 154. All data that have been collected were analyzed using multivariate statistical methods: the exploratory factor analysis and the multiple linear regression method. Three factor analyses (FA) were applied in order to determine the dimensions that, according to respondents, best define the implementation of the principles of the QMS and the implementation of SD principles through the implementation of sustainable practices, and to examine the existence of a statistically significant impact of such implementation on the economic, environmental and social aspects of business. The Kaiser – Meyer – Olkin (KMO) test was applied as a statistical measure to identify the suitability of the data for factor analysis and the results of the KMO test for each performed factor analysis are greater than 0,6. The first factor analysis (EFA 1) identified three dimensions (factors) that according to the respondents' perception, best describe and determine the implementation of the principles of the quality management system in hotel companies. The generated three factors explain 56,04 % of the total variance. The reliability of each generated dimension was determined by calculating the Cronbach alpha coefficient which was greater than 0,700. The second factor analysis (EFA 2) identified two dimensions (factors) which, according to the respondents' perception, best describe and determine the implementation of the principles of sustainable development in hotel companies. Those two factors explain 50,95 % of the total variance. The reliability of each generated dimension was determined by calculating the Cronbach alpha coefficient which was greater than 0,700. The third factor analysis (EFA 3) identified three dimensions (factors) that, according to the respondents' perception, best describe and determine the impact of the implementation of the principles of the quality management system and the principles of sustainable development on the economic, environmental and social aspects of the business performance of the studied hotel companies. The generated three dimensions explain 73,264 % of the total variance. The reliability of each generated dimension was determined by calculating the Cronbach alpha coefficient which was greater than 0,700. Three Ordinary Least Square regressions (OLS) were performed in order to test the hypotheses. In the regression model, the independent variables are the factors that were generated by the first and the second factor analysis (EFA 1 and EFA 2), and the dependent variables are the factors that were generated by the third factor analysis (EFA 3). In total three Ordinary Least Square regressions were performed, one regression model to test each hypothesis. In order to determine whether the independent variables are good predictors of the dependent variables for each regression model, the F-test was calculated using ANOVA. The F-test results in each regression model are significant. According to the results of the regression analysis and the established significance of the regression model, all three auxiliary hypotheses were confirmed. Furthermore, for all three regression models, the RESET test was applied and it confirmed that no variables were omitted in the regression models. According to the results of the research, the main hypothesis has been proven and confirmed: "The implementation of the quality management system and the principles of sustainable development have a statistically significant impact on the economic, environmental and social aspects of hotel business performance". The results of the conducted research are in line with the following previously conducted researches: Tari, et al. (2020); Abbas et al. (2020); Sunil et al. (2021); Ghaderi et al. (2019); Fioru et al. (2019); Alipour et al. (2019); Nguyen et al. (2018) confirming that the implementation of quality management system and the principles of sustainable development have a positive impact on the economic, environmental and social aspects of business performance. From the theoretical perspective, the scientific contribution of the doctoral dissertation results from the development of the scientific thought that connects the principles of the quality management system and the principles of sustainable development, and the impact of their implementation on the economic, environmental and social aspects of hotel business performance. Furthermore, the scientific contribution derives from the expansion of the theoretical knowledge in the field of quality management and sustainable development, as well as the expansion of the theoretical knowledge of the economic, environmental and social aspects of hotel business performance. The results of the scientific research proved which dimensions of the quality management system and sustainable development are relevant according to the respondents' perception in order to impact the economic, environmental and social aspects of hotel business performance, which represents the scientific contribution of the conducted research in an empirical sense. The applied contribution of the research comes from the applicability of the results in the hotel practice. The results of the scientific research identified which factors are relevant for measuring and monitoring the impact of the implementation of the principles of quality management systems and the principles of sustainable development on the economic, environmental and social aspects of hotel business performance. The results of the conducted scientific research can help the hotel managers in creating guidelines for the efficient integration of the quality management system and the principles of sustainable development into everyday business practice.