Necrotizing fasciitis (NF) is an infection characterized by necrosis of the superficial muscle fascia and surrounding soft tissues. It usually occurs following skin breaches from penetrating traumas or high-degree burns. Less frequently, it could be related to major abdominal surgery. However, no cases of thigh NF after minor abdominal procedures have ever been reported. A previously healthy 59-year-old male patient underwent a colonoscopic polypectomy. After the procedure, the patient developed an increasing right groin pain. The CT scan showed a gas collection in the right retroperitoneum space and in the right thigh soft tissues. Thus, a right colon perforation was hypothesized, and the patient was moved to the nearest surgery department and underwent a right hemicolectomy procedure. During surgery, the right thigh was also incised and drained, with gas and pus leakage. Nevertheless, the right lower limb continued to swell, and signs of systemic infection appeared. Afterward, clinical conditions continued to worsen despite the drainage of the thigh and antibiotic therapy, and the patient died of septic shock after just two days. This case shows that, although rare, lower limb NF should be considered among the causes of early post-operative local painful symptoms.