A 58-year-old woman was admitted to our hospital for repeated episodes of dry cough, low-grade fever, and gradual development of dyspnea on exertion. Chest computed tomography showed diffuse ground-glass opacities in both lung fields. Bronchoalveolar lavage fluid (BALF) showed an increased number of lymphocytes, and transbronchial lung biopsy revealed alveolitis and epithelioid cell granuloma. The acute onset and the patient's living environment suggested summer-type hypersensitivity pneumonitis. However, anti-Trichosporon antibody was negative and a definitive diagnosis could not be made. The patient's condition improved with corticosteroid treatment and, after discharge from the hospital, she moved to a new home. The following year, however, her symptoms returned, and she was readmitted to our hospital. Recurrence of the disease despite the change in environment ruled out summer-type hypersensitivity pneumonitis. Given the patient's history of budgerigar breeding five years earlier, bird breeder's lung was suspected. Anti-bird excreta antibody found in the patient's serum and BALF, along with a positive lymphocyte stimulation test against pigeon serum, strongly suggested an acute onset of bird breeder's lung. We report a rare case of acute bird breeder's lung with radiologic findings of ground-glass opacities, a one-year disease-free period and an acute relapse.