© 2019 Objective: The present study translated and adapted the Brazilian version of the Patient-Determined Disease Steps (PDDS) scale and tested its validity and reproducibility in Brazilian persons with multiple sclerosis (MS). Methods: The PDDS underwent translation and back-translation procedures for producing a Brazilian Portuguese version of the PDDS (PDDS/BR). Sixty-three patients with MS (48 females) completed the PDDS/BR and underwent a neurological examination for generation of Expanded Disability Status Scale (EDSS) scores. Participants further performed the following tests: Timed 25-Foot Walk (T25FW), Timed Up and Go (TUG), six-minute walk test (6MWT), Nine Hole Peg (9HPT), and Symbol Digit Modalities Test (SDMT). Construct validity of PDDS/BR scores was determined by Spearman correlation with EDSS, and comparison of correlations between PDDS/BR and EDSS with the functional tests. We examined overall correct classification of disability categories (i.e., mild, moderate, or severe disability) by the PDDS/BR in relation to the EDSS. Test-retest reproducibility of PDDS/BR scores was examined in a subsample of 31 participants after 15 days. Results: There was a strong relationship between the PDDS/BR and EDSS scores (ρ = 0.723, p < 0.05). The correlations with TUG, T25FW, 6MWT, and 9HPT were comparable for the PDDS/BR and EDSS scores. Overall correct classification of disability categories by the PDDS/BR was 79.3%. Results indicated excellent test-retest reproducibility for the PDDS/BR (Intraclass Correlation Coefficient= 0.911, 95% CI: 0.685–0.918). Conclusion: The PDDS/BR scores provide a valid and reliable assessment of mobility disability and may be used by researchers and neurologists to assess disability status in Brazilians with MS.