IgG4-related lung disease (IgG4-RLD) is a rare and chronic progressive autoimmune disease. We report a case of IgG4-related inflammatory pseudo-tumor of the lung that was seropositive for proteinase 3 anti-neutrophil cytoplasmic antibody (PR3-ANCA). A 61-year-old male had a mass lesion in the right lower lung field in chest X-ray. Transbronchial lung biopsy resulted in a pathological diagnosis of IgG4-RLD. The condition was improved by hormonal therapy.