Purpose. The aim of the study was to analyse the execution efficiency of core tactical principles in young soccer players and compare them among different game positions. Methods. The sample included 54 Brazilian young soccer players. Tactical performance was measured by the System of Tactical Assessment in Soccer with the GR3-3GR test in 3770 tactical actions. Friedman followed by Wilcoxon tests were used to analyse differences between tactical principles. Kruskal-Wallis and Mann-Whitney U tests were performed to compare tactical efficiency between defenders, midfielders, and forwards (p < 0.05). Results. Offensively, the results indicated that young players demonstrated less efficiency in executing the principle ‘depth mobility’ compared with ‘penetration,’ ‘offensive coverage,’ ‘width and length,’ and ‘offensive unity.’ Regarding the defensive aspects, ‘concentration’ was performed more efficiently than other principles. Comparisons between positions proved that midfielders and forwards executed ‘offensive unity’ more efficiently than defenders. Defenders tended to present high ‘defensive coverage’ efficiency when compared with ‘midfielders.’ Conclusions. High efficiency in the execution of ‘concentration’ represents an obstacle to make deep passes and hinders offensive movements between the last defender line and goal, given low efficiency of ‘depth mobility.’ Midfielders and forwards performed ‘offensive unity’ more efficiently than defenders. As for defensive principles, defenders presented better performance in ‘defensive coverage,’ giving support to the first defender. In practical applications, it is suggested that coaches of young regional soccer players carry out activities which allow depth passes to teammates as well as games to promote ‘offensive unity’ for defenders and ‘defensive coverage’ for midfielders.