A 69-year-old man was admitted to our hospital complaining of generalized weakness and cough for one month. Chest computed tomography (CT) demonstrated bilateral ground-glass opacities and a nodule in right S6 about 11mm in diameter with multiple mediastinal lymph node swellings. After admission the patient's symptoms improved without therapy and examination of the bronchoalveolar lavage fluid (BALF) and transbronchial lung biopsy (TBLB) revealed findings compatible with acute hypersensitivity pneumonitis. We did not consider that the acute hypersensitivity was caused by the patient's Amazon bird, because he had been breeding them for 40 years. However after obtaining a careful history, it became clear that close and frequent contact with the bird had occurred for the first time in the previous year. On the basis of the anti-bird excreta antibody found in the patient's serum and BALF, we diagnosed this case as a case of acute bird fancier's lung caused by the yellow-shouldered Amazon bird. We diagnosed the nodule in right S6 as lung adenocarcinoma by a thoracoscopic lung biopsy, and performed lower lobe lobectomy. We considered that the mediastinal lymph node swellings were caused by hypersensitivity pneumonitis.