Purpose: We aimed to examine whether pre-treatment, post-treatment and change in health-related quality of Life (HRQoL) is associated with survival, in patients with head and neck cancer (HNC). Methods: We included 948 newly diagnosed HNC patients treated with primary or adjuvant (chemo)radiotherapy with curative intent. The EORTC QLQ-C30 questionnaire was assessed pre-treatment and at 6 weeks, 6 months and 12 months post-treatment. Multivariable Cox regression analyses were performed to examine whether HRQoL at all time points and changes in HRQoL over time were associated with survival, after adjusting for demographic, clinical and lifestyle-related variables. Results: Higher HRQoL scores were significantly associated with improved 5-year overall survival at all time points, except for the subscale global QoL at 6 weeks. Changes in HRQoL at 6 weeks post-treatment compared to pre-treatment were not significantly associated with survival. Changes in physical (HR: 0.88 95% CI: 0.82–0.96) and emotional functioning (HR: 0.90 95% CI: 0.85–0.96) from pre-treatment to 6 months post-treatment and changes in global QOL, and physical, emotional, and social functioning from pre-treatment to 12 months post-treatment were significantly associated with survival. Conclusion: Higher HRQoL reported pre-treatment and post-treatment (6 weeks, 6 months and 12 months) are significantly associated with improved survival, as well as changes in HRQoL at 6 and 12 months compared to pre-treatment. Our results highlight the value of monitoring HRQoL and to identify those patients that report decreased or deteriorated HRQOL. This may help to further improve cancer care in a timely and efficient manner.