Objective Analyze the demographics, clinical characteristics, efficacy and safety of natalizumab treatment in Brazilian patients with multiple sclerosis (MS) followed up for at least 12 months, in two tertiary MS care centers in São Paulo.Method We evaluated the effect of natalizumab treatment on annualized relapse rate and disability progression in 75 patients with MS treated with natalizumab for at least 12 months. A subgroup analysis was performed to evaluate efficacy of natalizumab treatment in patients with Expanded Disability Status Scale (EDSS) ≤ 3.0 vs patients with EDSS > 3.Results Patients treated for at least one year with natalizumab showed a 91% reduction in aRR, as well and an improvement in neurological disability. The impact of natalizumab treatment was greater in patients with EDSS < 3.0. Overall, natalizumab was safe but one patient developed progressive multifocal leukoencephalopathy.Conclusion Natalizumab as a third line therapy is safe and efficacious, especially in patients with mild neurological disability.