To achieve common training goals and achievements, coaches must be aware that the increasing achievements of their athletes are related to supporting factors for achievement. For achieving optimal achievement, there are many factors, one of which is the supporting factor related to fluid needs. In this article, researchers focus on athletes’ knowledge of fluids related to hydration status. Fluids have a significant impact on the performance of athletes in achievement. This study aims to determine the level of knowledge of hydration status in talented athletes in junior category sports. This study is an observational study with a cross-sectional study design. The population is talented athletes of the junior category sport. The measurement test of each variable is to use a closed questionnaire that has been tested for validity and reliability. The results of this study showed that the level of knowledge of athletes about the need for body fluids (hydration) in the athlete’s category is less than as many as 1 respondent or 1.2%. The category is enough as many as 10 respondents or 11.9%. The good category was 64 respondents or 76.2%. The category was excellent as many as 9 respondents or 10.7. Knowledge of hydration status is essential. Thus, it is advisable to provide training knowledge of the athlete’s hydration status.