Purpose: There are many factors affect shoulder performance in tennis players. The aim of this study was to investigate the relationship between upper extremity performance parameters and shoulder rotator muscle strength in adolescent tennis players. Methods: Thirty-one adolescent tennis players, who were aged between 10 to 18 years, were included in the study. Medical ball throw, closed kinetic chain upper extremity stability test and handgrip strength test were used to determine upper extremity performance. Shoulder rotator muscle strength was evaluated using ISOMED 2000 (D&R GmbH, Germany) isokinetic system. Linear regression analysis was used for statistical analysis. Results: There was a moderate positive correlation between medicine ball throw distance and 60°/s internal rotator (IR) peak torque (PT) (r=0.535, p=0.002) and external rotator (ER) PT (r=0.421, p=0.018). A strong correlation was found between the handgrip strength and 60°/s IR-PT (r=0.647, p=0.001) and ER-PT (r=0.645, p=0.001). The closed kinetic chain upper extremity stability test results were related with 60°/s ER-PT (r=0.391, p=0.029). Conclusion: Upper extremity performance increased as the shoulder muscle strength increased in adolescent tennis players. Determining the factors affecting performance in tennis players in adolescent period is very important to increase performance and to prevent future injuries.