Acute eosinophilic pneumonia (AEP) is characterized by febrile illness, diffuse pulmonary infiltrates with eosinophilia. The pathogenesis is not well understood. We report a case of 22-year-old men who never smoke presented with AEP 2 days after acute passive smoke exposure. He developed acute respiratory failure despite having no history of the disease. Computed tomography of the lung revealed diffuse bilateral pulmonary infiltrates. Lung biopsy specimens revealed marked eosinophil infiltration in the alveolar septa without signs of vasculitis. Two days prior to the disease, he was exposed to cigarette smoke for 2 hours in a closed area. In the absence of other causes, passive smoking may cause lung inflammatory responses. The level of urinary cotinine, which is a biomarker of smoke exposure, was considerably higher (0.198 μg/ml [201 ng/mg Creatinine]) than that in nonsmokers, but never detected following period. This case suggests that short-term passive smoking may cause AEP.