Left-sided portal hypertension due to splenic vein stenosis is a very rare disease. We report a case of this condition in a 21-year-old woman who suffered from a first episode of tarry stool passage with fresh blood vomiting. Panendoscopy showed isolated gastric varices while sonography showed a normal liver but the presence of splenomegaly with prominent collateral circulations. Further imaging studies, including abdominal computed tomography, splenoportography and percutaneous transhepatic portography, revealed a focal stenotic proximal splenic vein resulting in left-sided portal hypertension. The collateral circulation ran from the short gastric veins via the left gastric veins into the main portal vein. The intraportal venous pressure was within normal limits. Splenectomy was performed and near normal wedge liver biopsy pathology confirmed non-cirrhotic extrahepatic portal hypertension. The patient had no further variceal bleeding after surgery.