Small-sided games are a method of soccer training in which the size of the field and the number of players are reduced. These games provide coaches with a useful tool with multiple applications to achieve the desired results. The objectives of this review were to determine what types of physiological effects and internal and external loads in particular are produced by the intervention of reduced games in professional or amateur soccer players, determining whether they are a good choice of training method. The results with the reduced games program obtain performance improvements in passing ability, sprint repetition, change of direction, and vertical jump. As a conclusion, the application of reduced games is a good way to optimize the time in the session by bringing together all the elements that occur in soccer, without sometimes producing the demanding physical demands of competition.