Abstract: Meylan, CMP, Cronin, JB, Oliver, JL, and Rumpf, MC. Sex-related differences in explosive actions during late childhood. J Strength Cond Res 28(8): 2097–2104, 2014—The purpose of this study was to examine sex-related differences in explosive actions during late childhood, while accounting for body size and maturity, and determine the predictive model responsible for performance. Sixty-eight boys (11.0 ± 1.1 years) and 45 girls (11.3 ± 0.9 years) performed a vertical and horizontal jump, 30-m sprint, and change of direction (COD) time trial. After allometric analysis, a common sex scaling factor of body mass was used for vertical (b = 1.02) and horizontal (b = 0.97) power. No significant sex difference in relative leg power was found before and after controlling for maturity status. Gender differences in 10 m, the Zigzag section, and flying 10 m of the COD task were found significant once adjusted for maturity (p ≤ 0.05). However, boys performed better than girls in 20- and 30-m sprint and the COD time trial regardless of maturity status (p ≤ 0.05). Reduced endomorphy in boys was the best predictor of explosive actions (R2 = 7–22%), whereas female performance was best explained by mass and maturity status (R2 = 15–19%). Jump power–specific allometric scaling factors need to be determined to account for body size. A training emphasis on sprinting and COD at a younger age in girls compared with boys is recommended because of their earlier onset of puberty and reduced natural ability in these tasks. Somatotype, age, maturity, and body mass should be monitored during the development of youth athletes to better understand explosive performance.