Objective: To translate and culturally adapt the Oxford Shoulder Score (OSS) to the European Portuguese language, and to test its reliability (internal consistency, reproducibility and measurement error) and validity (construct validity). Methods: The OSS Portuguese version was obtained through translations, back-translations, consensus panels, clinical review and cognitive pre-test. Portuguese OSS, Disabilities of the Arm, Shoulder and Hand (DASH) questionnaires, and the visual analogue scales of pain at rest [VAS rest] and during movement [VAS movement] were applied to 111 subjects with shoulder pain (degenerative or inflammatory disorders) and recommended for physical therapy. A clinical and sociodemographic questionnaire was also applied. Results: The reliability was good, with a Cronbach’s alpha coefficient of 0.90, an intraclass correlation coefficient (ICC) of 0.92, a standard error of measurement (SEM) of 2.59 points and a smallest detectable change (SDC) of 7.18 points. Construct validity was supported by the confirmation of three initial hypotheses involving expected significant correlation between OSS and other measures (DASH, VAS rest and VAS movement) and between OSS and the number of days of work absenteeism. Conclusion: The Portuguese OSS version presented suitable psychometric properties, in terms of reliability (internal consistency, reproducibility and measurement error) and validity (construct validity).