Situs inversus totalis (SIT) is a rare congenital anomaly that refers to a completely reversed location of the abdominal and thoracic organs. We report the case of 50-year-old man with gastric cancer and SIT who was diagnosed during a screening esophagogastroduodenoscopy. A chest X-ray, abdominopelvic computed tomography, and 18F-fluoro2-deoxyglucose-D-glucose-positron emission tomography scans revealed SIT. We performed a radical subtotal gastrectomy with D2 lymph node dissection. Advanced surgical skill is required to perform a precise lymphadenectomy in a patient with SIT by visualizing the exact mirror image of the anatomy during the operation. The patient had an uneventful intra- and postoperative course and was followed up at the outpatient department without any evidence of recurrence. In conclusion, surgery in a patient with gastric cancer and SIT can be safely performed by paying attention to the inverted anatomic structures during the operation.