This study examined long-term health utility and symptom-toxicity trajectories among patients with head and neck cancer (HNC).For patients diagnosed with HNC (2014-2019), Health Utility Index 3 (HUI-3), Edmonton Symptom Assessment Scale (ESAS), and MD Anderson Symptom Inventory (MDASI) surveys (including both the core and head and neck cancer modules) were prospectively collected at multiple time points (at the baseline, after surgery, during radiotherapy, and 3, 6, 12, and 24 months after treatment). Locally estimated scatterplot smoothing plots were generated to describe HUI-3, ESAS, and MDASI trajectories over time by clinicodemographic factors, treatment modality, and tumor subsite. Contributions of clinical factors were assessed with univariable and multivariable analyses.In 800 patients, the treatment modality and the tumor subsite produced unique HUI-3, ESAS, and MDASI trajectories. Patients treated with surgery alone experienced rapid improvements in HUI-3, ESAS, and MDASI scores postoperatively. Among patients treated with chemoradiotherapy, patients with nasopharyngeal carcinoma had greater declines in HUI-3 during treatment in comparison with patients with oropharyngeal carcinoma, but they had similar ESAS/MDASI scores. Among patients treated with radiotherapy, patients with laryngeal carcinoma had better HUI-3/ESAS/MDASI scores than those with oropharyngeal carcinoma during treatment, but they slowly converged after treatment. Female sex, an age > 75 years, a household income < $40,000, a Charlson comorbidity score > 1, an Eastern Cooperative Oncology Group performance status > 0 (at the baseline), and current smoking were independently associated with worse HUI-3 trajectories. HUI-3 had mild to moderate correlations (ρ = 0.2-0.5) with individual symptom-toxicity trajectories.Long-term HUI-3 trajectories are associated with tumor subsite, clinicodemographic, and treatment factors, and this may be partly explained by relationships with symptoms/toxicities. Separate evaluations by subsite and treatment should occur in health utility and symptom-toxicity studies of HNC.This study indicates that the long-term health utility and symptoms/toxicities of patients with the most common head and neck cancers (ie, squamous cell carcinomas and nasopharyngeal carcinomas) differ over time with a variety of factors, including the tumor anatomic site, treatment volume, clinicodemographic characteristics (eg, age, human papillomavirus status, tumor stage, gender, smoking status, alcohol status, education, and comorbidities), and treatment modalities. Generalizations across all head and neck cancers should be strongly discouraged. Future studies should evaluate health utility, symptoms and toxicities, and patient need assessments separately for each anatomic site and treatment modality.© 2021 American Cancer Society.