Athletes face varying levels of anxiety during competitions and competitions. This state of anxiety in athletes can manifest itself both before, during and after the competition. When the literature is examined, the effect of anxiety in athletes on sports performance is explained by the Yerkes-Dodson Law developed by Yerkes and Dodson. This law proposes an inverted U-shaped relationship between anxiety and performance. In summary, this law states that very low or very high anxiety levels can negatively affect the performance of athletes, while athletes' optimal performance during competition is associated with a moderate level of anxiety. In this context, the effect of anxiety on sports performance is discussed in this book chapter.