Aims: Natalizumab is approved as an infusion every 4 weeks (standard-interval dosing [SID]) in relapsing-remitting multiple sclerosis (MS). Extended-interval dosing (EID) reduces risk of progressive multifocal leukoencephalopathy (PML) compared with SID, but the impact on healthcare resources and costs remains unknown. Methods: In this population-based study, we included 208 natalizumab-treated MS patients who were classified into EID (≤15 infusions in the previous 18 months; n = 51; age = 33.7 ± 11.1 years; female = 72.5%) and SID (>15 infusions in the previous 18 months; n = 157; age = 36.5 ± 10.8 years; female = 68.1%) groups. Results: Natalizumab EID had fewer MS outpatient visits (p = 0.01) and related costs (p = 0.03), and lower natalizumab costs (p < 0.01) compared with SID, without changes in other healthcare resources and costs. Conclusion: Natalizumab EID is associated with reduced direct treatment costs, apparently without additional healthcare burden.