Laparoscopic sleeve gastrectomy (LSG) has become the dominant bariatric procedure because of its reliable weight loss and low complication rate. Portomesenteric vein thrombosis (PMVT) after LSG is an infrequent complication that can lead to serious consequences. Here, we report a patient who presented with abdominal pain 11 days after LSG for the treatment of morbid obesity. Contrast CT of the abdomen revealed PMVT. The patient had liver cirrhosis, which is a major risk factor for PMVT. When LSG is performed on an obese patient with liver cirrhosis, careful attention must be paid to the onset of PMVT.