Research question: The objective of this paper is to examine the level of the development of spa tourism with a special review of the wellness tourist offer of the Republic of Serbia, and also which factors of this tourist offer we should pay special attention to and improve, to achieve the highest level of tourist loyalty. Motivation: The tourism potential of the Republic of Serbia has not been sufficiently researched and that served as a basic motivational factor. Idea: Considering the tourist potential that Serbia has and partly the work of Han et al., (2017), the fact that spa tourism is the fastest-growing sector in the entire tourism industry, and that the wellness tourism offer is a very important segment of spa tourism, there is a need to identify factors that influence the visitors' loyalty formation for such tourist destinations. As the Republic of Serbia has a lot of wellness centres, it represents a very convenient location for conducting such research. Data: This research included 298 guests of wellness centres in Vrnjačka Banja: "Solaris", "Aleksandar", "Merkur", "Zepter", "Kralj", "Slatina" and "Iwa Wellness Centre". Data collection was performed during July and August 2019. Methods: The PLS-SEM method was used in this paper to test the defined research hypotheses. Factors that contribute to loyalty and revisit for the wellness and spa tourist destination were investigated, and they were measured by the appropriate number of questions: quality of wellness and spa tourism, the value of wellness and spa services, attraction of wellness and spa tourist destination and satisfaction with wellness and spa tourist destination. All attitudes were measured using a five-point Likert scale. Results: The quality and value of wellness and spa services positively impact the affection for wellness and spa tourist destination and satisfaction with wellness and spa tourist destination, while the attraction of wellness and spa tourist destination positively affects satisfaction with wellness and spa tourist destination and tendency to revisit by tourists. The existence of a positive influence of satisfaction with wellness and spa tourist destination and the desire to revisit the tourist loyalty formation was also shown. Contribution: Improving the quality, value, and effect with the Republic of Serbia as a wellness and spa tourist destination will increase the satisfaction of visitors and their desire to revisit this tourist destination, which will lead to greater loyalty in the future. This will increase the revenue generated from this type of tourism and accelerate local and regional development.