We present a rare case of solitary pulmonary papillary adenoma. A man consulted our hospital because of abnormal chest radiography finding. Chest computed tomography demonstrated a well-defined, homogeneous nodular shadow 11 mm in size at the left lower lobe. The previous physician had considered it to be an old benign inflammatory granuloma and had kept it under observation. This mass was followed through chest radiographs at annual medical checkups for 4 years. In 2006, enlargement and lobulation were noted. We performed thoracoscopic partial resection of the left lower lobe. On postoperative pathology examination, the nodule was found to be a circumscribed nodule consisting of a papillary growth of cuboidal to low-columnar epithelial cells lining the surface of a fibrovascular stroma. The histological features were consistent with pulmonary papillary adenoma. Only 20 cases of pulmonary papillary adenoma have been reported in the literature.