AbstractAcute diverticulitis is one of the most common gastrointestinal illnesses that requires hospital admission. It has a broad range of presentations from uncomplicated disease to perforation and peritonitis that require emergent surgical exploration. Abscesses are one of the most common complications. We present a case of retroperitoneal abscess with extension to the antero-lateral upper thigh that was successfully treated with open Hartman’s procedure with drainage of psoas abscess and open drainage of thigh abscess.