Mycophenolate mofetil (MMF) is an immunosuppressive agent (IS) which is widely prescribed in neuromyelitis optica spectrum disorder (NMOSD) patients. We aim to assess the efficacy and safety of MMF in controlling relapse and disease severity. Eligible studies obtained from the EMBASE and Ovid MEDLINE databases were studies of NMOSD patients treated with MMF, which reported treatment outcomes as Annualized Relapse Rate (ARR) or Expanded Disability Status Scale (EDSS) before and after treatment. Fifteen studies included 1047 patients, of whom 915 (87.4%) were aquaporin-4 immunoglobulin seropositive. The total number of patients that received MMF was 799. A meta-analysis on ARR was conducted in 200 patients from 4 studies and on EDSS in 158 patients from 3 studies. The result showed a significant improvement with a mean reduction of 1.13 [95% confidence interval (CI) 0.60-1.65] in ARR, and a mean reduction of 0.85 (95% CI 0.36-1.34) in EDSS after MMF therapy. Adverse events occurred in 106 (17.8%) of 594 patients during MMF therapy. This systematic review and meta-analysis showed that using MMF as a preventive therapy in NMOSD patients can significantly reduce relapse rates and improve disease severity with acceptable tolerability.