In the conditions of global competition, companies are forced to grow and develop, and to maintain their competitive advantage by continuously innovating and delivering value to consumers superior to the competition, whereby the quality of services has a key role. Application of marketing activities within the company becomes more and more important today, to create in a more successful way a positive working atmosphere, to choose and maintain an employee who will provide quality service within the company for the benefit of all. Furthermore, hotels must encourage employees to embrace certain behaviors that go beyond their regular job functions, such as helping customers resolve problems, cooperating with colleagues, preventing unexpected incidents, and paying extra attention to organization. In other words, hotel employees should not only do their jobs but they should also go above and beyond their own obligations towards the hotel and others. This self-initiated and positive employee behavior is called organizational citizenship behavior (OCB). In the literature, there is a lack of theoretical and empirical research and results, which explore the relationship between internal service quality, internal marketing and organizational citizenship behavior. This is precisely the reason why this dissertation systematically analyzes and deals with relevant theoretical notions based on the sources from national and international scientific literature, concerning internal service quality in the hospitality industry, and provides an elaborate overview and analysis of the obtained preliminary results and notions based on the conducted empirical research. Based on the results obtained here, a standardized and coherent model was developed and tested, which makes it possible for the impact that internal market orientation and organizational citizenship behavior have on the achievement of internal service quality in the hospitality industry to be measured. The aim was to determine the relationship between internal service quality and the concepts of internal market orientation and organizational citizenship behavior, furthermore, to analyze the difference in the respondents' (hotel employees') perception of the internal service quality, organizational citizenship behavior and internal market orientation in relation to the chosen demographic characteristics, to analyze cause-and-effect relationship of the observed concepts, to test the validity and reliability of the imported measuring instrument and finally to provide guidelines for the application of the conceptual model and the results in practice. By conducting conceptual and empirical research and by applying statistical methods of data analysis, all the set aims and all the set hypotheses have been achieved. The results of this research support the suggested model of achieving internal service quality in the hotel industry and confirm the main scientific hypothesis of this dissertation that there is a positive relationship between internal market orientation, organizational citizenship behavior and internal service quality in the hospitality industry. The theoretical notions from the conceptual part of the research suggest that, in the hospitality industry, the quality of products and services depends on the knowledge, skills, experience, appearance, behavior and other characteristics of the employees in that company. As stated in the literature review, educated, professionally trained, highly motivated and loyal employees create and maintain quality, which affects the guests' satisfaction and the success of the hotel. In order to achieve high level of services and products, it is necessary to have satisfied employees because they are the only ones who can create a good relationship with the customers and offer a higher level of service. The way employees treat guests depends on how they feel in their workplace. The assessment of employees' satisfaction in scientific research is studied from various aspects and by applying various methodologies. The research review shows that the beginnings of measuring this concept are related to the measuring of the service quality. For the purposes of measuring the internal service quality construct, this paper used the modified SERVQUAL model, which evaluates four dimensions: reliability, assurance, empathy, responsiveness. Previous studies point out that the success of internal service quality depends on the successful application of internal marketing within a company and its activities. This is the best way to offer quality to employees, that they will in return transfer to customers. The job performed by a satisfied employee raises the level of productivity of the hotel company, which contributes to the company's competitiveness. Employees should constantly be encouraged to perform high-quality work. This is possible only if the goals set by thecompany are clearly stated to the employees, if business processes and their role in these processes are clearly defined, and if feedback on the results is enabled (how good or bad something is done). This is possible with the application of internal marketing activities, i.e. internal market orientation, which guarantees continuous training of employees and improvement of internal service quality. In this dissertation, internal market orientation is observed through three dimensions suggested by Ruizalba i suradnici (2014.) who studied hotel service in Spain. The first dimension (generation of internal market intelligence), is composed of two different factors: value exchange between company and employees, and internal segmentation; the second dimension (exchange of internal market intelligence), and the third dimension (response to internal market intelligence) comprises three factors: training of employees, management concern and work-family balance. Furthermore, successful application of internal market orientation not only increases job satisfaction and organizational commitment but also results in voluntary behavior in the workplace. When employees are authorized to take on responsibilities for certain jobs, to make decisions and improve business processes, they feel more involved and want to improve their job performance. The application of organizational citizenship behavior contributes to achieving the service quality both in internal and external market. This paper analyzes five dimensions that include employee's behavior, which is not required in his/her job description: conscientiousness, altruism, civic virtue, sportsmanship and courtesy. To test the hypotheses and the possibilities for improvement and enhancement of the methodology of the measuring concepts in this dissertation, a research was conducted in hotels in Dubrovnik. The preliminary results were collected with a questionnaire that was developed based on the extensive review of the relevant literature. The questionnaire comprises three constructs: internal service quality, organizational citizenship behavior and internal market orientation. The respondents rated the variables using a 5-point Likert scale. A pilot study was conducted in June 2017 on a representative sample. The respondents successfully completed the survey, and in the main research, only minor changes were related to the place, i.e. the location and age and sex. The main research was conducted in eight hotels, in the period between July and September 2017. The survey is based on 201 correctly filled in questionnaires. To obtain the best quality of the information from the gathered data, three levels of statistical analysis were used: univariate, bivariate and multivariate statistical analysis. The results of descriptive statistical analysis show that hotel employees gave relatively high grades to the perceived internal service quality. They gave slightly lower average grades to organizational citizenship behavior, whereas the lowest grades were given to the application of internal market orientation in the hotel. Correlative analysis was conducted with the goal of determining the relationship between the constructs of application and measurement of internal service quality in the hotel. Statistically significant relationship exists between internal service quality and internal market orientation (r=0,709), whereas the relationship between internal market orientation and organizational citizenship behavior is weaker with the coefficient of r=0,355 and that is the reason why H3 is partly accepted. By applying the method of multiple regression, the relationship between internal service quality and the concepts of internal market orientation and organizational citizenship behavior was confirmed. To show the possibility of statistically significant differences between the constructs regarding demographic characteristics, Kruskal Wallis and Mann Whitney U tests were used. The results of the analysis show that there are no statistically significant differences regarding: sex, age and the area of education, whereas marital status and the level of education of the hotel employees partly affect the rating of the “internal service quality” concept. It is also necessary to point out that there are certain limitations to this research. This research, as most marketing research studies are, is conducted over a certain period of time, in this case at the peak of the tourist season, and the survey among the hotel employees during a longer period (pre-season and post-season) would contribute to a greater reliability of the results. A certain limitation is also the size of the sample and its structure, and to generalize the results better, the research should be conducted in other tourist destinations in Croatia as well. Furthermore, possible incomprehension of the questions might represent a possible weakness of the conducted research. Therefore there is a possibility for the future study to create new questionnaire and implement factor analysis and asses the conceptual model with the partial least squares structural equation modeling (PLS-SEM). Despite all that, the mentioned limitations do not diminish the contribution of the results in X the theoretical, methodological and applicability sense. The suggested concept has not yet been noted in the national or foreign literature, hence this paper sets grounds for future research. In the applicability sense, new notions regarding the importance of the application of internal marketing activities, i.e. internal market orientation and organizational citizenship behavior with the aim of achieving internal service quality in a hotel organization, can help the hotel management to achieve business goals to the satisfaction of all the participants in the business processes.