The aim of this study was to evaluate the function of a cohort of patients with rheumatoid arthritis (RA) from the core set of the International Classification of Functioning and Health (ICF) for RA over 12 months. We used prospective longitudinal data to conduct a cohort study among a well-characterized group of RA patients. Ninety RA patients aged between 40 and 70 years were included in the study. Patients were evaluated at baseline and after 12 months. Age, disease duration, current smoking, erosions, disease activity, functional test, disability and physical activity were evaluated. Then, the ICF core set classification for RA was applied. 81 patients completed the assessments, the majority of patients were female (88.9%) and the mean age was 56.5 ± 7.3 years. At baseline, the median disease activity was 3.0. There was a statistically significant (p < 0.02) improvement in "Exercise tolerance functions" over 12 months and also a statistically significant (p < 0.001) decrease in "Muscle strength functions" over 12 months. The activity and participation domain showed a weak correlation with the clinical data of the DAS28-PCR (p<0.02). We conclude that relevant aspects of the ICF Core Set for RA were able to adequately express the physical and functional factors of the RA cohort. This tool provides a common language for the interdisciplinary team, which can enhance the use of timely interventions to prevent physical disability in clinical practice.