A 37-year-old man with fever, cough, and dyspnea with no medical history developed an eosinophilic pleural effusion and blood eosinophilia. No evidence of malignancy or pathogens was detected in the pleural effusion, and the pleural specimen obtained by thoracoscopy showed eosinophilic infiltration with inflammatory granulation tissue without fibrinoid necrosis or malignant cells. Since a myeloproliferative disorder was also excluded, the diagnosis was idiopathic eosinophilic pleurisy. Corticosteroid treatment was started and then slowly tapered, and the eosinophilic pleural effusion resolved. Considering the various etiologies of eosinophilic pleurisy, a practical clinical approach to the investigation and diagnosis of eosinophilic pleurisy is presented.