Duodenal and jejunal varices usually occur due to portal hypertension and are rare causes of gastrointestinal tract bleeding. We report the case of a patient with no clinically significant history of a coagulopathy disorder, cirrhosis, or portal hypertension who presented with duodenal and jejunal varices that resulted in lower gastrointestinal bleeding with superior mesenteric vein thrombosis. Mesenteric angiography revealed superior mesenteric vein thrombosis and varices at the fourth part of the duodenum and the proximal jejunum draining into the main portal vein, but no active bleeding source was recognized. The patient was hemodynamically unstable. Emergency laparotomy was performed and revealed duodenal and jejunal varices, with occlusion of the superior mesenteric vein. Partial resection of the duodenum and jejunum and end-to-end anastomosis were performed. After surgery, the patient was hemodynamically stable with no recurrence of bleeding.