Oral mucositis (OM) is a common acute side effect during radiotherapy treatments for head and neck cancer (HNC), with a potential impact on patient's compliance to therapy, quality of life (QoL) and clinical outcomes. Its timely and appropriate management is of paramount importance. Several quantitative scoring scales are available to properly assess OM and its influence on patient-reported outcomes (PROs) and QoL. We prospectively assessed OM in a cohort of HNC patients submitted to radiation using the Oral Mucositis Assessment Scale (OMAS), while its impact on PROs and QoL was evaluated employing the Oral Mucositis Weekly Questionnaire-Head and Neck Cancer (OMWQ-HN) and the Functional Assessment of Cancer Therapy-Head and Neck Cancer (FACT-HN). Evaluation of OMAS scores highlighted a progressive increase in OM during treatment and a partial recovery after the end of radiation. These trends were correlated to PROs and QoL as evaluated with OMWQ-HN and FACT-HN questionnaires. In the present study, we provided a quantitative assessment of OM, PROs and QoL in HNC patient undergoing radiotherapy, potentially useful for future comparison.