Introduction: The oral cavity can be a site for pathological manifestations of many diseases and their treatments. One example is the head and neck cancer (HNC). Main treatment modalities for HNC are surgery, radiotherapy and chemotherapy. Head and neck cancer treatment by radiotherapy may induce pathological conditions in the oral cavity, both during treatment and after its conclusion. This case report described oral assessment before radiotherapy on a patient with HNC and briefly reviewed radiotherapy oral sequelae. Case Report: A 56-year-old female was referred to the oral medicine clinic at Cipto Mangunkusumo National Hospital for evaluation and elimination of oral infection foci prior to radiotherapy for HNC. The patient underwent a thorough oral examination, where we noted poor oral hygiene with several necrotic dental roots, teeth requiring extractions, multiple dental caries, and ill-fitting denture with denture stomatitis. A treatment plan was generated, and the patient received proper dental management and was informed about the possibility of oral complications related to radiotherapy. Conclusion: In patients with HNC, radiotherapy can induce various pathological conditions within the oral cavity, potentially decreasing the patient's quality of life and compromising treatment outcomes. However, those conditions can be mitigated or prevented by oral precautions, elimination of infection sources, and maintenance of good oral hygiene. © 2020 by Nova Science Publishers, Inc. All rights reserved.