Pylephlebitis is a rare complication of intra-abdominal infections and describes thrombosis and infection as two different pathophysiological phenomena in the cause of this disease. The nonspecific presentation of disease makes its diagnosis difficult and thus leads to high mortality. The treatment comprises antibiotics and also includes controversial use of anticoagulation in these patients. Here, we present a patient with past medical history of human immunodeficiency virus and past diverticulitis who presented with fever, chills, diarrhea, neck pain, and photophobia. He was diagnosed with acute sigmoid diverticulitis with associated inferior mesenteric vein thrombophlebitis. He improved after intravenous antibiotics and anticoagulation and was discharged. He underwent sigmoid colectomy 3 months after his initial presentation and was advised to take anticoagulation for a total of 6 months.