BACKGROUND: Poor lumbopelvic-hip control has been linked to higher shoulder and elbow joint moments and injury risk in collegiate and professional baseball pitchers. The purpose of this study was to investigate if lumbopelvic-hip control was correlated with shoulder and elbow joint moments and drive leg ground reaction force (GRF) in high school baseball pitchers. The hypothesis was that poorer lumbopelvic-hip control would be correlated with higher joint moments and lower drive leg GRF. Study design: Cross-sectional study. METHODS: Lumbopelvic-hip control was assessed based on the anterior-posterior pelvis angular displacement using the single-leg lift test (SLLT) on each limb. Peak shoulder horizontal adduction and internal rotation and elbow varus moments during pitching were calculated using inverse dynamics. The correlations between lumbopelvic-hip control and the biomechanical variables (i.e., normalized joint moments, peak anterior GRF, and anterior GRF impulse) were analyzed. RESULTS: Sixty healthy high school pitchers (age: 15.8 ± 1.3) recruited from local baseball training facilities participated. The lumbopelvic-hip control while standing on the drive leg had a moderate correlation with the peak shoulder horizontal adduction moment during pitching (r=.301, p=0.02) but not with peak shoulder internal rotation moment (p=0.19), elbow varus moment (p=0.95), peak anterior GRF (p=0.95), or anterior GRF impulse during the drive (p=0.61). Lumbopelvic-hip control while standing on the lead leg was not correlated with any variables. CONCLUSIONS: Poorer lumbopelvic-hip control was moderately correlated with greater shoulder horizontal adduction moment during throwing among high school baseball pitchers. These results support and extend the understanding of the influence of lumbopelvic-hip control on pitching mechanics in high school-aged pitchers. LEVEL OF EVIDENCE: Level 3.