Background. As a component of the sports industry, professional athletes are always faced with challenges, including injury, performance loss, etc. To overcome these problems, many famous athletes have turned to build their brands, as it enables them to create and maintain a market of customers and fans. Objectives. The purpose of this study was to use the Grounded theory approach to design a model of the micro factor affecting personal brand development for Professional athletes. Methods. The present study was an applied research with a descriptive-survey method, and a library-field data collection method. This research was a qualitative research and was carried out using the Grounded Theory method. In the present study, semi-structured interviews were used as data gathering tools. Sampling was done using judgmental sampling method and followed up to theoretical saturation, which included a total of 18 interviewees. Results. Based on the findings, after three stages of open coding, selective coding, and theoretical coding, a total of 62 concepts, 11 categories, and 4 factors were obtained that showed "Athlete's Behaviors", "Athlete's Personality Traits", "Marketable Lifestyle" and "Athletic Performance" play an important role in developing the personal brand for professional athletes. Conclusion. By identifying the factors affecting the personal brand of professional athletes, athletes, managers, and marketers can create and maintain a market for their customers and fans, achieve sustainable income and maintain reputation and popularity.