12045 Background: The survival rate of patients with nasopharyngeal cancer (NPC) has significantly improved in the last decade. However, there are only a few studies that have quantified the long-term morbidity and mortality that follow NPC treatment. This study aims to analyze the chronic health conditions, all-cause mortality, and cause-specific mortality among NPC survivors. Methods: The Hong Kong NPC Survivor Study (HKNPCSS) is a retrospective cohort study conducted across all six oncology centers in Hong Kong. It included longitudinal follow-up of 5-year survivors diagnosed with NPC between 1997 to 2015. We compared the standardized mortality ratio (SMRs) of 7893 survivors to a matched population in terms of age, sex, and calendar year. We also calculated the frequencies of chronic conditions of 7893 survivors and 23679 healthy individuals with matched age, sex, and date of cohort entry. Chronic health conditions were classified using the Common Terminology Criteria for Adverse Events. Cox proportional hazard models were used to estimate hazard ratios (HRs) for chronic health conditions. Results: The mean age of NPC survivors was 49.1 years, while healthy individuals had a mean age of 50.5 years. Among the 7893 NPC survivors, the 20-year cumulative all-cause mortality was 34.0% (95% CI, 29.1%-38.9%), with 1668 (59.9%) of 2785 deaths attributed to health-related causes. The SMR for NPC survivors compared to the general population was 3.81 (95% CI, 3.67-3.95), with the highest SMRs observed for pulmonary (SMR: 6.18, 95% CI, 5.73-6.64) and cardiovascular (SMR: 2.12, 95% CI, 1.90-2.36) causes. Among the survivors, 59.2% (n=4674) had severe, life-threatening, or fatal (grade 3-5) health conditions, with a 20-year cumulative incidence of 59.0% (95% CI, 56.4%-61.5%). The adjusted hazard ratio (HR) of grade 3-5 chronic condition in NPC survivors, compared to healthy cohorts, was 7.02 (95% CI, 6.64-7.42). Gastrointestinal (HR: 20.7), hearing, visual, and nasal (HR: 15.4), and neurological (HR: 8.39) conditions had the highest risks. Intensity modulated radiotherapy (IMRT), compared to non-IMRT, was associated with reduced risks of all-cause mortality (HR: 0.83, 95% CI, 0.74-0.91) and a trend towards reduced grade 3-5 chronic health conditions (HR: 0.89, 95% CI, 0.75-1.05). Conclusions: Even 20 years after diagnosis, NPC survivors still face increased risks of late mortality and morbidity. The findings emphasize the need for a comprehensive survivorship program to improve outcomes for NPC survivors.