This study investigated the objectivity, reliability, and the validity of the Basketball Throw Test (BTT) as an upper-body muscular strength measure. Participants (33 boys and 32 girls; mean age = 8.75 ± 1.47) performed the BTT on 2 occasions (1-week apart), and the hand-grip test as criterion measure. The objectivity and reliability were estimated using an intraclass correlation coefficient (ICC2,1) and graphically examined according to the Bland-Altman approach. Pearson correlation coefficient and the known-differences method was employed to determine validity. The BTT demonstrated high objectivity ICC2,1 = 0.90 (95% CI, 0.84-0.94), reliability ICC2,1 = 0.91 (95% CI, 0.86-0.95) and validity (r = 0.77, p <0.001). The Bland-Altman method graphically confirmed intraclass correlation data. The significant difference in the BTT scores between 6-year-old children (1.61 ± 0.23) and 10-year-old children (t = -12.64, p < 0.001) provided additional support of validity. The BTT test is a feasible measure of upper-body muscular strength in school-aged children.