Immunosuppressive drugs are the milestone of treatment of autoimmune diseases, but they can lead to serious complications, including hepatitis B virus reactivation in HBV carriers as well as in patients with occult HBV infection (OBI). A 36-year-old man with OBI was diagnosed with pemphigus vulgaris. He was prescribed prednisolone and his hepatitis B surface antigen turned positive. Viral replication was successfully controlled by lamivudine and adefovir. Mycophenolate mofetil and intravenous immunoglobulin were not effective in controlling the pemphigus vulgaris. The patient received rituximab 500 mg weekly for four weeks and went into remission without any adverse effect. He safely received another course of rituximab after a relapse one year later. In conclusion, testing for hepatitis B core antibody should be considered mandatory, in addition to HBsAg, for the screening of pemphigus patients to detect rare cases of OBI before starting therapy. Furthermore, rituximab may in some cases be safely used in HBV carriers using antivirals concomitantly.