We report a case of hypersensitivity pneumonitis and asthma attack caused by isocyanates in a 61-year-old man. The patient was admitted for diagnosis and treatment of workday fever, cough, wheezing, and dyspnea. He worked in a furniture manufactureing factory and used polyurethane adhesive containing isocyanates. His chest CT showed diffuse centrilobular shadows. Findings of bronchioalveolar lavage fluid were compatible with hypersensitivity pneumonitis, and specific IgE was positive for toluene diisocyanate, 4,4’-methylenediphenyl diisocyanate, and 1,6’-hexamethylene diisocyanate. The diagnosis of asthma was established by positive bronchial reversibility and bronchial hyperresponsiveness. Furthermore, an elevation of the fraction of exhaled nitric oxide (FeNO) level also supported the diagnosis of bronchial asthma. The workplace environmental challenge induced cough, shortness of breath, chest tightness, increases in body temperature, WBC, and CRP and decreases in peak expiratory flow rate and SpO₂. We interpreted these results as positive for both hypersensitivity pneumonitis and asthma. Of interest is that the environmental provocation test decreased the level of FeNO.