This study aimed to examine sex-specific differences in the execution of key technical aspects of upper-body kinematics in the volleyball spike, such as arm cocking in the back swing, a high elbow in the forward swing, and joint angles during ball contact. In addition, upper-body strength and shoulder mobility were tested to elaborate their association with spike kinematics. A total of 77 male and female volleyball players’ kinematics were analyzed via 3D-motion capturing during spiking. Strength and mobility were assessed through machine-based maximum trunk strength tests, the upper quarter Y-balance test, glenohumeral internal rotation deficit, and the shoulder mobility test of the functional movement screen. Bayesian t-tests of each variable evaluated sex differences. Multiple linear regressions were calculated separately for male and female athletes to identify predictors for spiking kinematics. Male athletes showed greater torso rotation in the backward swing and reduced shoulder mobility, while female athletes demonstrated a more vertical elbow position in the forward spike swing and superior dynamic stability in the upper quarter Y-balance test. Trunk strength and dynamic stability significantly predicted the level of arm cocking in males, while shoulder mobility was their main predictor for a high elbow in spiking. In females, a high elbow was predicted by upper-body dynamic stability. No significant predictors could be identified for kinematics during ball contact in either sex. The findings highlight sex-specific kinematic patterns in spike execution and demonstrate that strength and mobility differently enact volleyball spiking in male and female players.