This chapter will present the findings of several studies that have investigated the momentary mood states of Brazilian football players in pre-competition situations, emphasizing the role of psychological aspects that have been studied in the literature. The data were obtained by Engelmann’s Present Mood States List, a Brazilian instrument to access subjective states. In these studies, mood states were related to variables such as playing position of the athletes, location of the competition, sequences of games and training sessions during the season, behavioural repertoire, and technical performance in the games. There is a common mood profile of football players in the moments before the game begins (interest, happiness, and hope); however, there are differences especially between defensive and forward players in different competitive contexts. Behavioural repertoire changes were related with pre-competitive mood states, revealing emotional and motivational components of the athletes’ performance. Factors such as Fatigue, Interest, and Serenity varied during the sequences of games and training. Young Brazilian football players feel a high level of pressure for winning, showing relief after victories (more than happiness or pride) and humiliation and shame after defeats. The present chapter focuses on the importance of considering positive aspects of an athlete’s mood and their interaction with emotional, motivational, and social aspects, expanding the understanding of the influence of psychological variables on human performance in sport. Practical implications, especially for coaches and sport psychologists, and future research directions are discussed.