A 29-year-old man was admitted to our hospital complaining of cough, wheezing, dyspnea, and fever one month after handling paint spray containing isocyanate (MDI). Chest HRCT findings showed diffuse ground-glass attenuation in both lung fields. A pulmonary function test revealed restrictive impairment, and the reversibility test was positive. His symptoms, HRCT findings, and pulmonary dysfunction were improved only after the cessation of isocyanate administration. BALF showed lymphocytosis, and the pathological findings of the TBLB specimen revealed cellular alveolitis, but no Masson bodies or epitheloid cell granuloma. As a result of environmental provocation, fever, hypoxia, and reduced peak expiratory flow developed, and the environmental provocation test was positive. The specific antibodies against MDI and TDI were positive in both serum and BALF, and the lymphocyte stimulation test against MDI was positive in peripheral blood. Combined hypersensitivity pneumonitis and bronchial asthma due to isocyanate were therefore diagnosed. Pulmonary dysfunctions due to isocyanate are known to include bronchitis, bronchial asthma, and hypersensitivity pneumonitis. However, case reports of combined hypersensitivity pneumonitis and bronchial asthma due to isocyanate are rare.