Afferent loop syndrome (ALS) is a rare complication of Billroth-II gastrojejunostomy. Most cases of ALS are caused by obstruction from adhesions, kinking at the anastomosis, internal hernia, stomal stenosis, malignancy, or inflammation surrounding the anastomosis. A 61-years old man, who had undergone gastric resection 30 years before, was admitted at emergency room with severe abdominal pain in acute onset, nausea and vomiting. Ultrasonography and multi-detector computed tomography suggested acute ALS, due probably to adhesions or internal hernia. The patient was conducted to digestive endoscopy unit and successfully treated with endoscopic decompression of dilated afferent loop. Open surgery is actually considered the gold-standard in treatment of ALS. However, some surgeons report a few cases treated by laparoscopic surgery, interventional radiology techniques, endoscopic decompression. Authors suggest endoscopic decompression of acute ALS due to adhesions or internal hernia as the first treatment, especially in high-surgical-risk patients.