IgG4-related disease (IgG4-RD) is a novel clinical disease entity characterized by elevated serum IgG4 concentrations, tissue infiltration by IgG4-positive plasma cells and formation of pseudotumor with fibrosis. Occuurence of IgG4-RD has been described in multiple sites, from salivary glands, thyroid gland, pancreas and bile duct retroperitoneum. IgG4-RD with pseudotumor of the larynx is extremely rare, with only 5 cases reported in the literarure until date. A 62-year-old female patient was admitted to our hospital with a submucosal tumor in the right supraglottic area. Biopsy was performed under general anesthesia twice. The histological findings showed only fibrosis and chronic inflammatory plasma cells. However, the serum IgG4 level was clearly elevated to 1460 mg/dl. In addition, immunohistological staining of the larynx, parotid gland and lymph node confirmed the diagnosis of IgG4-RD. Treatment was started with a high dose of prednisolone (0.6 mg/kg/day) for 2-4 weeks, with tapering of the dose subsequently tapered to 8 mg/day. About 3 days after the initiation of treatment, the pseudotumor of the larynx disappeared completely. This case is only the sixth report of the association of IgG4-RD with pseudotumor of the larynx. The initial symptom in all patients was hoarseness, and only one gave a history of dyspnea. All the case had been treated with prednisolone and showed improvement of the laryngeal symptoms, except in one case which developed persistent vocal cord immobility. There is an urgent need for prompt treatment when the larynx is involved, considering the potential for irreversible damage. Long term follow-up and careful check up of whole body are required.