A three-year-old Labrador Retriever presented to a local veterinary practice for acute onset of dyspnea with no known history of trauma or underlying pulmonary disease. Thoracic radiographs indicated bilateral pneumothorax. Over the following seven weeks, conservative management with intermittent thoracocentesis provided only temporary improvement in signs and the dog was referred to the Cornell University Hospital for Animals for further evaluation. Repeat thoracic radiographs confirmed a persistent pneumothorax and CT imaging indicated a small bulla on the caudal part of the left cranial lung lobe. An exploratory thoracotomy confirmed the diagnosis and the single lesion was resected via partial lung lobectomy. Histopathology confirmed a focal subpleural pulmonary bulla with no evidence of underlying pulmonary disease. The dog recovered well from surgery and was discharged to the care of her owners four days post-operatively. One year later she continues to do well with no reported recurrence of respiratory signs.