Abstract Background: The Indian Takayasu Clinical Activity Score (ITAS2010) was developed in 2010 as an assessment tool for disease activity in patients with Takayasu arteritis (TA). It has since been widely used in different studies and in clinical practice for the management of patients with TA. The present study aims to translate the ITAS2010 into Brazilian Portuguese language and to validate it for use in clinical practice in Brazil. Methods: For this cross-sectional study, the ITAS2010 was translated in accordance with the guidelines described by Beaton et al. and then applied with 27 patients with TA on three assessments by two rheumatologists working independently. To measure interrater agreement, the assessments were performed on the same day within approximately 1 hour. One of the rheumatologists performed a second evaluation of patients with TA within 7 to 14 days to measure intrarater agreement. Results: The correlation coefficient for the ITAS2010 score between the two raters was high (r =0.916; p < 0.0001), as well as the intraclass correlation coefficient (ICC) [0.918 with a 95% confidence interval (95CI): 0.828-0.962]. The correlation coefficient and the ICC for intrarater agreement were moderate for ITAS2010 (r =0.633; p < 0.0001 and ICC = 0.594; 95CI: 0.292-0.790). The ITAS2010 at baseline was compared with the physician's global assessment (PGA) and with Kerr's criteria for detecting disease activity in TA. Higher ITAS2010 scores were observed in patients with active and grumbling/persistent disease than in those presenting inactive disease according to the PGA [1.5 (0.0-3.0) vs. 0.0 (0.0-0.0); p = 0.0025]. Patients with active disease according to the Kerr's criteria had also higher ITAS2010 scores than those considered in remission [3.0 (3.0-7.0) vs. 0.0 (0.0-0.0); p = 0.0068]. Conclusions: The Brazilian Portuguese version of the ITAS2010 is a valid and reproducible tool for the assessment of disease activity in TA and it is an additional tool for the routine evaluation of Brazilian patients with TA.