Background <p>The Upper Limb Rotation Test is an upper limb performance assessment specific to overhead throwing that requires shoulder control and stability, while incorporating the entire kinetic chain. The purpose of this study is to investigate the reliability of the Upper Limb Rotation Test (ULRT) in adolescent male basketball players.</p> Methods <p>This study was conducted with 51 male basketball players at Hanibal Sports Club. It is an intra-rater reliability study. The Upper Limb Rotation Test was administered twice under the same conditions with a one-week interval. Intra-rater reliability was quantified using ICC (two-way mixed-effects, absolute agreement), Bland–Altman analysis, the standard error of measurement (SEM), and the 95% minimal detectable change (MDC).</p> Results <p>The intra-rater reliability of the test was found to be ICC = 0.93 for the dominant extremity and ICC = 0.96 for the nondominant extremity (p &lt; 0.001). The SEM value was found to be dominant extremity 1.38, nondominant extremity 0.89, while the MDC value was found to be dominant extremity 3.82, nondominant extremity 2.46. Bland–Altman plots showed homoscedastic scatter with a small negative bias (retest slightly higher) and few points marginally outside the 95% limits of agreement.</p> Conclusions <p>Among adolescent male basketball players, the ULRT is a clinician-friendly, easily administered, and practical test for assessing upper-extremity rotation in a kinetic-chain position, and it can be reliably applied in this population.</p> Trial registration <p>This study is prospectively registered at NCT06269601 (clinicaltrials.gov) (Registration Date: 27/02/2024).</p>