Well-differentiated fetal adenocarcinoma (WDFA) histologically resembles pulmonary blastoma, and is thought to be a subtype of pulmonary blastoma which has differentiated epithelial features resembling the fetal lung among its epithelial features and sarcomatous features. We recently encountered one patient who underwent surgery for WDFA. This case is reported with a discussion of the literature. A 33-year-old woman had a tumor shadow in the lower lobe of the right lung. The tumor was diagnosed as pulmonary blastoma as a result of echographic biopsy, and right total pneumonectomy was performed. No sarcomatous features were observed on postoperative histological assessment, and the patient was diagnosed as having WDFA. Its prognosis is believed to tend to be better than that of biphasic blastoma, in which sarcomatous features are mingled with epithelial features. However, it is reported that chemotherapy or radiotherapy has seldom been effective. Complete surgical resection is essential for long-term survival.