Pivotal trials showed the effectiveness of the monoclonal antibody ocrelizumab in relapsing and progressive multiple sclerosis (MS). However, data on everyday practice in MS patients and markers of treatment effectiveness are scarce. We aimed to collect real-world data from ocrelizumab-treated MS patients, relapsing-remitting (RR) and progressive MS patients (PMS), including active secondary progressive MS (aSPMS) and primary progressive MS (PPMS) patients, and to explore potential prognostic factors of clinical outcome. Patients were enrolled at MS centres in the Campania region, Italy. We collected clinic-demographic features retrospectively one year before ocrelizumab start (T−1), at ocrelizumab start (T0), and after one year from ocrelizumab start (T1). We explored possible clinical markers of treatment effectiveness in those patients receiving ocrelizumab treatment for at least one year using multilevel-mixed models. We included a total of 383 MS patients (89 RRMS and 294 PMS; 205 females, mean age: 45.8 ± 11.2, disease duration: 12.7 ± 11.6 years). Patients had a mean follow-up of 12.4 ± 8.2 months, and 217 patients completed one-year ocrelizumab treatment. Overall, EDSS increased from T−1 to T0 (coeff. = 0.30, 95% coefficient interval [CI] = 0.19–0.41, p < 0.001) without a further change between T0 and T1 (p = 0.61). RRMS patients did not show an EDSS change between T−1 and T0 nor between T0 and T1. Conversely, PMS patients showed EDSS increase from T−1 to T0 (coeff. = 0.34, 95% CI = 0.22–0.45, p < 0.001) without a further change between T0 and T1 (p = 0.21). PMS patients with a time from conversion shorter than 2 years showed increased EDSS from T−1 to T0 (coeff. = 0.63, 95% CI = 0.18–1.08, p = 0.006) without a further change between T0 and T1 (p = 0.94), whereas PMS patients with a time from conversion longer than 2 years showed increased EDSS from T0 to T1 (coeff. = 0.30, 95% CI = 0.11–0.49, p = 0.002). Naïve patients showed an EDSS decrease between T0 and T1 (coeff. = −0.30, 95% CI = −0.50–−0.09, p = 0.004). In conclusion, our study highlighted that early ocrelizumab treatment is effective in modifying the disability accrual in MS patients.