Otorhinolaryngologists often encounter and treat adolescents and young adults (AYA; aged 15–39 years) with cancer. Thus, it is important for them to recognize the impact of cancer treatment on the fertility of patients from this generation. In this retrospective review, we evaluated 60 AYA patients who were diagnosed with head and neck cancer at our department. Regarding the risk of gonadal toxicity due to cancer treatment, according to the classification by The Japan Society of Clinical Oncology Clinical Practice Guidelines 2017 for Fertility Preservation in Childhood, Adolescent, and Young Adult Cancer Patients, one and three patients were found to be at high and intermediate risks, respectively. However, the risk of gonadal toxicity was not adequately explained in the guidelines; hence, they need to be revised. To preserve the fertility of AYA patients with head and neck cancer, patient information should be shared with appropriate obstetrics and gynecology or urology specialists before treatment. Furthermore, it is important to build a reproductive medicine network and ensure prompt collaboration with oncologists before initiating cancer treatment.