Background and aims Endometriosis is a gynecologic recurring persistent condition affecting from 8% to 15% of premenopausal women worldwide. About 80% of women with endometriosis have at least one form of chronic pain – a multidimensional experience influenced by a number of psychosocial factors, including pain-related beliefs. The Survey of Pain Attitudes is the most commonly used measure of pain-related beliefs. This study aims to evaluate the psychometric properties of a Portuguese version of a brief version of the SOPA (the SOPA-35) in a sample of Portuguese women with Endometriosis. Methods A sample of 199 Portuguese women with Endometriosis provided demographic and pain history information, and completed a Portuguese version of the SOPA-35 and measures of pain intensity, disability, and psychological function. Analyses were performed to evaluate the factor structure of the Portuguese SOPA-35 items as well as the internal consistency, composite reliability, convergent validity, and concurrent validity of the scale scores. Results Confirmatory factor analysis supported a six-factor solution for a 19-item version of the Portuguese version of the Survey of Pain Attitudes (SOPA-19-P). The six scales evidenced marginal to good reliability (Cronbach's alphas: between 0.60 and 0.84; composite reliability: between 0.61 and 0.84). Four scales evidenced acceptable to good convergent validity (AVE: between 0.51 and 0.63). The findings also supported the concurrent validity of the SOPA-19-P. Conclusions The results support the use of the Portuguese SOPA-19-P for research and clinical purposes with Portuguese women in chronic pain due to endometriosis. Future research is warranted to further develop a European Portuguese version of SOPA. Implications The findings provide psychometric information about the SOPA-19-P. The results are helpful to researchers wishing to study the role of pain-related beliefs and their association with adjustment and treatment outcomes in women with chronic pain due to endometriosis.