Background: Copenhagen hip and groin outcome score (HAGOS) is the only valid and reliable self-reported questionnaire for assessing symptoms and activity limitations of subjects with hip and groin problems. The aim of this study was to translate and culturally adapt the English version of the HAGOS to Persian and to evaluate its reliability in young athletes with hip and groin pain. Methods: This cross-sectional study was performed in Tehran University of Medical Sciences, School of Rehabilitation, Iran, from June 2014 to May 2015. In order to develop the Persian HAGOS, the English HAGOS was translated and culturally adapted into Persian language based on the standard forward-backward translation and expert committee review. Then, for the test-retest reliability investigation, young male athletes suffering from hip and groin pain, recruited from sport physical therapy clinics, completed the Persian HAGOS two times with 1-2 weeks interval. Independent samples t‐test and Intraclass correlation coefficient (ICC) was used to determine the test-retest reliability of the six subscales and the total score of Persian HAGOS. The SPSS statistical software (IBM SPSS, Armonk, NY, USA) was used for all analyses. Results: Fifty young male athletes, mean age 26.12±3.37 years (range: 18-33), participated in this study. ICC value for test retest reliability of total score was 0.74 (95% CI: 0.59-0.84). ICC values for subscales scores ranged from 0.6 for participation in physical activities subscale to 0.79 (P<0.0001) for pain subscale (P<0.0001). There were no significant differences between the test and retest scores obtained for subscales and total scores (t-test, P>0.05). Conclusion: The HAGOS was successfully translated and cross-culturally adapted from English into Persian language. The Persian version of HAGOS is a reliable questionnaire for the evaluation of young athletes with hip and groin pain in clinics and research.