The aim of this paper is to present and explain the specifics of the fitness preparation of tennis players during the competitive period. In order to achieve top results, tennis players and their coaches look for the smallest details that can improve the game and help achieve results. In tennis, periodization is different from other sports. This is due to the competition calendar, the change of the playing surface, and the large number of trips. The problem is evident especially with the fitness training as there is a great number of tournaments played during the year in which the player has to be in a good shape, so there is not enough time for a proper preparation period, while it is necessary to pay attention to an adequate recovery as well. Tennis belongs to a group of acyclic polystructural sports that requires a high level of fitness preparation so that tennis players can optimally present their technical and tactical abilities. Each fitness professional will face particular, specific challenges when working with tennis players, whether it be different anthropological characteristics of tennis players, working in different weather conditions and zones on different surfaces within a short time or questions about how long a tennis player will stay at the tournament and how to plan their recovery. All this requires fitness trainers to have an extraordinary amount of knowledge, experience and ability to adapt to new situations. The purpose of this paper is to highlight the specificities that tennis as a sport possesses, i.e. tennis players as athletes, which is further reflected in the course, plan and program of fitness training.