Cases of foreign body ingestion are encountered relatively often in clinical settings; however, serious complications are rare. In such cases, mediastinal abscess due to esophageal perforation can become a life-threatening complication. We encountered two cases of severe complications due to an esophageal fish bone foreign body. The first case was a 40-year-old male with an intramural esophageal abscess due to a fish bone after eating fish five days before visiting the hospital. The patient underwent surgical treatment, but the esophageal abscess did not improve; so, the abscess was drained through endoscopic mucosal dissection, and the abscess improved. In the second case, a 64-year-old male, who had eaten fish three days before visiting the hospital, had esophageal perforation by a fish bone, and abscess formation in the mediastinum and the lesser sac in the abdominal cavity were observed. Although surgical treatment was performed, the intra-abdominal abscess formation was not controlled; so, percutaneous drainage (PCD) was inserted, and the abscess improved. Both patients were discharged without any complications. Here, we report two cases that were improved through surgical treatments and additional treatments such as endoscopic dissection and PCD.