Introduction:Iliopsoas abscess (IPA) is a rare infection in the iliopsoas muscle compartment that occurs from primary or secondary causes [1]. Primary IPA is due to an infectious organism’s hematogenous or lymphatic spread from a distant site. Secondary IPA is due to the direct expansion of an infectious process into the iliopsoas muscle [2]. The majority of cases are due to secondary causes, which include Crohn’s disease, diverticulitis, appendicitis, colorectal carcinoma, UTI, instrumentation, osteomyelitis, sacroiliitis, septic arthritis, trauma, endocarditis, hepatocellular carcinoma, and femoral artery catheterization [3]. They often present with non-specific symptoms, leading to diagnostic delays. The condition is commonly secondary to abdominal surgery, with 75–85% occurring as a complication of it [4]. Second is Crohn’s disease, where internal fistulae occur in up to 15% of patients [5]. Other causes include gastrointestinal malignancies, with 0.3%–0.4% of patients with colon cancer [6].The treatment involves a multidisciplinary team, including gastroenterologists, surgeons, and infectious disease specialists, as many cases are complex. The treatment recommendations vary depending on the severity and etiology of the IPA. In this case report, we discuss a rare incidence of iliopsoas abscess due to a fistula from the sigmoid colon caused by the patient’s complex history of cancer, chemotherapy, and radiation treatment, which was closed by an endoscopic clip.