Idiopathic necrotizing fasciitis (NF) is an infrequent, highly lethal skin infection that spreads rapidly, marked by fascia and subcutaneous tissue necrosis. It occurs in the absence of a known causative factor. Its emergence after sterile orthopedic fixation with unexpected spread to the abdomen may turn to be challenging both as a medical and surgical emergency. A 56-year-old diabetic female presented with multiple fractures. After open reduction and internal fixation (ORIF) with iliac crest grafting of hip fracture, she developed incisional NF which later spread to the abdomen. Post-ORIF of hip fracture complicated with idiopathic NF and abdominal spread. She underwent emergency débridements with negative pressure wound therapy and broad-spectrum intravenous antibiotic therapy. After granulation, the wounds were closed with skin flaps and grafts with antibiotic beads. When the NF spread to the abdomen, additional débridements during abdominal explorations were performed. The patient was initially stable with promising healings of the wounds. Later, the patient suddenly developed a high fever and severe abdominal pain. Ultrasound revealed that NF emerged unexpectedly in the right lower abdomen. The causative agent of the NF remained undetected. Despite all the extensive treatments, the patient's condition deteriorated rapidly. She died of septic shock and multiple organ failure. The idiopathic NF may still potentially occur after a clean ORIF of the hip region. The implementation of intensive guideline-based treatments may show improvements, but the risk of unexpected NF spread to the abdomen should be anticipated, which may increase the mortality rates in diabetic or immunocompromised patients.