<p>Head and neck cancers represent approximately 5% of all malignant tumors. Radiotherapy is a primary treatment option but can induce significant toxicities affecting oral health and quality of life. This study evaluated the feasibility and potential benefits of providing written oral hygiene instructions to patients to prevent or manage dental and oral complications in head and neck cancer patients. This prospective, single-center, feasibility study included 44 patients with head and neck cancer requiring radiotherapy who had a dental plaque index ≥ 30%. A dental assistant provided oral hygiene education and a written information guide. The primary outcome was improvement in oral hygiene defined as a reduction of ≥ 30% in dental plaque index at 3 months post-radiotherapy. Secondary outcomes included evolution of plaque index, patient satisfaction, and motivation toward oral health. Of the 44 patients initially included, 32 were evaluable for the primary outcome (9 died before final assessment, 1 refused follow-up, 1 did not follow study procedures and 1 did not undergo radiotherapy). At 3 months post-radiotherapy, 65.6% of patients demonstrated a ≥ 30% reduction in dental plaque index. There was a notable increase in the frequency of tooth brushing (from 21.9% to 48.4% brushing three times daily) and mouthwash use (from 53.1% to 75%). Regular dental check-ups increased from 68.8% to 78.1%. 97% of patients were satisfied with the clarity of information in the guide, and 97% with its comprehensiveness. This feasibility study suggests that providing written oral hygiene instructions, combined with patient education/consultation, shows promise for improving oral hygiene practices among head and neck cancer patients undergoing radiotherapy. The high level of patient satisfaction and maintained motivation toward oral health indicate the potential value of this approach in oral supportive care. ClinicalTrials.gov Identifier NCT05494970 (https//clinicaltrials.gov/study/ NCT05494970).</p>