Left portal hypertension and splenic vein occlusion commonly occur with pancreatic tumors, however these signs are rarely observed in patients with acinar cell carcinoma. This report describes a rare left portal hypertension in a patient who presented with a dilated esophagogastric vein upon esophagogastroduodenoscopic examination of a gastric polyp. A contrast-enhanced computed tomography scan revealed a pancreatic tumor, with obstruction of the splenic vein and portal-systemic shunt. The patient was diagnosed with an acinar cell carcinoma of the pancreatic tail. This patient highlights that pancreatic acinar cell carcinoma should be considered as a differential diagnosis in patients with a dilated esophagogastric vein and without signs of liver disease.