In the field of radiotherapy, there is very little scientific data on the management of nonagenarians, especially in patients aged 90 years or more and with head and neck cancer (HNC). We made one of the first retrospective study of the feasibility and safety of radiotherapy in this population with HNC. Records of radiotherapy coming from four health facilities were studied to include all nonagenarian patients with HNC in the last 10 years and who received radiation therapy. We analyzed patient characteristics and primary cancers, as well as objective of the treatment (curative or palliative), efficacy and toxicity. Twenty patients receiving radiotherapy were identified; mean age was 93.2 years (standard deviation 2.8). Treatment was given with curative and palliative intent in 40 and 60 % of cases, respectively. The most common primary tumors were tumors of the salivary glands (30 % of cases), oral cavity tumors (25 % of cases) and thyroid tumors (15 % of cases). Median total prescribed dose was 47.5 Gy (12-70 Gy). Median number of delivered fractions was 18.5 (2-35 fractions). All patients received intensive supportive care during radiotherapy. Toxicities were mild to moderate. Radiotherapy could not be completed for four patients (20 % of cases). One patient developed grade 1-2 delayed toxicities. At the last follow-up, only four patients (20 % of cases) were alive. Cancer was cause of death in most cases. Radiotherapy may be performed for the nonagenarians with HNC. The total dose and fractionation must be adjusted to optimize the tolerance. However, the prognosis remains very poor, cancer being the main cause of death. Research of geriatric vulnerabilities prior to any treatment, in the context of a comprehensive geriatric assessment, is still recommended to select patients for radiotherapy.