Aim: Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disease resulting in cognitive impairment, physical disabilities, and neurological symptoms. Ocrelizumab is an effective drug used in MS treatment. However, it causes a risk of hepatitis B reactivation in anti-HBc positive patients. We describe the impact of entecavir and tenofovir on HBV reactivation during treatment with ocrelizumab. Materials and methods: Our study included eight patients (aged 18-70 years) with positive anti-HBc antibodies who were diagnosed with MS based on the 2017 McDonald criteria. The subjects were treated with ocrelizumab and were given anti-HBV prophylaxis with nucleoside analogs. The mean time from the beginning of therapy with nucleoside analogs to the initiation of ocrelizumab treatment was 27.5 days. Patients were administered ocrelizumab and none of them was diagnosed with HBV reactivation. Results: None of the laboratory parameters worsened. No severe adverse effects were observed. These results suggest that entecavir and tenofovir are effective in HBV reactivation prophylaxis. Additionally, positive anti-HBc antibodies do not rule out treatment with ocrelizumab. Conclusions: In patients with positive anti-HBc antibodies, nucleoside analogs, such as entecavir or tenofovir, should be administered before ocrelizumab administration to reduce the risk of viral reactivation. Further studies on simultaneous treatment with ocrelizumab and nucleoside analogs are required to confirm our findings.