INTRODUCTION: Fibular grafts are commonly used in reconstructive head and neck surgery, and several complications have been reported. Tibial stress fracture, however, is rare. PATIENT: A 65-year-old woman presented with a tibial stress fracture 10 weeks after a vascularized fibular flap had been harvested for a mandibular defect due to osteoradionecrosis. The main symptom was activity-related pain after a period of no complaints. CONCLUSIONS: One should be aware of the complications, particularly after weeks or months, in cases of activity-related pain in the lower extremities. Prevention can be implemented by an awareness of the need to build up the muscles for supporting the tibia in the initial healing phase.