Esophageal cyst is a relatively rare disease and about 91 cases have been reported in Japan. We report a new case of esophageal cyst. Tha patient was a 36-year-old male who complained of nausea and vomiting. We performed esophagography, endoscopy, endoxcopic echography, CT and MRI and found a cystic lesion in the lower esophagus. We made the diagnosis of an esophageal cyst and performed operation. The tumor was in the esophageal muscle but did not have a commissure to the esophageal lumen. We extirpated it with esophageal muscle and repaired the muscle defect with diaphragma. This tumor, 7.5×5.0cm in size, was a monolocular cyst and contained brown muddy material. Microscopic findings revealed a ciliated columnar epithelium and squamous epithelium in the cyst wall but cartilage was not found. The cyst was covered with double smooth muscle layers. It was difficult to differentiate an esophageal cyst from a paraesophageal bronchogenic cyst but these histological findings suggested that this cyst was an esophageal cyst.