Background: The evaluation of sexual function is an important outcome in women who suffer some pelvic floor disorders (PFD). The Female Sexual Function Index (FSFI) is the most widely used questionnaire to evaluate the sexual health in female population. This study presents the adaptation and psychometric validation of the FSFI for Spanish women with PFD. Methods: The Spanish version of the FSFI was developed through the forward and backward translation process. The psychometric properties of reliability, validity, responsiveness, and feasibility were conducted in Spanish women with PFD who were assigned to the case or control group (with or without sexual dysfunction respectively). Results: A total of 323 Spanish women with PFD were recruited. The cross-cultural adaptation of the Spanish FSFI achieved a good semantic, conceptual, idiomatic, and content equivalence. The test-retest reliability was shown to be high in all of the cases. The convergent validity showed high results in the domain intercorrelations between each domain and total FSFI. The discriminant validity showed statistically significant differences between sexual dysfunction and control groups. The responsiveness was shown to be moderate to good in the dimensions and excellent in the total FSFI. Conclusions: Spanish FSFI can be used as a reliable, valid, responsive, and feasible instrument for assessing sexual function in women.