The decision-making process about how to rehabilitate edentulous osseous defects in patients with head and neck cancer history can be complex. Even though, endosseous dental implants could be considered to be the first choice for treating these patients, it is highly important to be aware of the complications that might occur. The aim of this report was to describe the clinical features of mandibular fracture after dental implants placement on a cancer irradiated patient and update the available information about this event. The case describes a 70-year-old man, with medical background of radiotherapy in jaw bones to treat a carcinoma in the floor of the mouth and later on in the soft palate and cheek. One week after dental implant surgery, the patient presented a mandibular osteoradionecrosis that healed in 8 months. A fracture on the right side of the body mandible was diagnosed one year after implant placement. Although several options were suggested in order to repair the fracture, the patient did not accept any further treatment despite the callus formation not being radiographically evident. The implant-supported prosthesis is functionally useful for more than 8 years of follow-up without significant problems. The implant treatment and management of oncologic irradiated patients require special considerations due to the risk of osteoradionecrosis and its possible complications, such as pathologic fracture. It is necessary to provide full information to the patient about risk factors and complications.