<bold>Purpose.</bold> The aim of this article was to analyze the relationship between tactical behavior and affective decision making of U-17 youth soccer players. <bold>Methods.</bold> The sample was comprised of 154 participants meeting the study inclusion criteria. Players played 4-min games on four-person teams (including goalkeeper) on a small-sided soccer field. The System of Tactical Assessment in Soccer (FUT-SAT) was used to determine the defensive tactical actions performed by players according to five different tactical principles. A total of 6140 defensive tactical actions were recorded. Their affective decision-making was measured by a computerized card task, the Iowa Gambling Task (IGT). <bold>Results.</bold> Significant negative correlation was found between players’ learning curve and the incidence of actions based on the principle of concentration. Less impulsive players presented a lower incidence of actions tied with the principle of concentration in comparison with more impulsive players. <bold>Conclusions.</bold> The findings suggest that, in the defensive phase, players who are less impulsive decision makers may benefit from more secure and stable defensive styles.