We report the case of a young woman with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, without tumor, who was successfully treated with rituximab. Because conventional immunotherapy, including corticosteroids, immunoglobulin (IVIg), and plasma exchange showed little improvement in our patient, we introduced another treatment using rituximab. A week after the first administration of rituximab, her symptoms improved gradually and significantly. This case provides in vivo evidence that rituximab is an effective agent for treating anti-NMDAR encephalitis, even in those cases where conventional immunotherapies have been ineffective. Rituximab should be regarded as a beneficial therapeutic agent for this disease.