This study aimed to investigate the contribution of specific kinematic indicators to the accuracy of the backhand high serve in squash among elite U-19 players. Using a descriptive approach combined with 2D biomechanical video analysis, ten successful serve trials performed by five nationally ranked players were recorded and analyzed with high-speed cameras and Simi Motion software. The research focused on the moment of impact, examining variables such as segmental velocities of the racket, limbs, and trunk to determine their predictive power on serve accuracy. The regression analysis revealed that the vertical velocity of the racket’s midsection, the vertical velocity of the right leg, and the velocities of the elbow, left knee, and right shoulder significantly contributed to serve accuracy, with contribution rates exceeding 55% up to 96%. These findings provide novel insights into the biomechanical determinants of a critical squash skill, highlighting the importance of coordinated lower and upper body mechanics. The study bridges a gap in performance analysis within racket sports and offers practical implications for coaches aiming to refine technical execution and serve strategy in competitive settings.