BACKGROUND: The Score Committee of the European Foot and Ankle Society (EFAS) developed, validated, and published the EFAS Score in ten languages (English, German, French, Italian, Polish, Dutch, Swedish, Finnish, Turkish, Portuguese). From other languages under validation, the Portuguese version completed data acquisition and underwent further validation.METHODS: The Portuguese version of the EFAS Score was developed and validated in three stages: 1) item (question) identification (completed during initial validation study), 2) item reduction and scale exploration (completed during initial validation study), 3) confirmatory analyses and responsiveness of Portuguese version (completed during initial validation study in nine other languages). The data were collected pre-operatively and post-operatively at a minimum follow-up of 3 months and mean follow-up of 6 months. Item reduction, scale exploration, confirmatory analyses and responsiveness were executed using classical test theory and item response theory.RESULTS: The internal consistency was confirmed in the Portuguese version (Cronbach's Alpha 0.84). The Standard Error of Measurement (SEM) was 0.27 and is similar to other language versions. Between baseline and follow-up, 69.4% of patients showed an improvement on their EFAS score, with adequate responsiveness (effect size 0.64).CONCLUSIONS: The Portuguese EFAS Score version was successfully validated in patients with a wide variety of foot and ankle pathologies. All score versions are freely available at www.efas.net.