Rationale: No studies have prospectively evaluated self-reported health-related quality of life (HRQOL) in the long-term after childhood-onset epilepsy. The objective of this study was to prospectively delineate self-reported HRQOL of adolescents and young adults (AYAs) eight and ten years after an epilepsy diagnosis and evaluate the degree of AYA-parent agreement in ratings of AYA’s HRQOL. Methods: Data came from the Health-Related Quality of Life in Children with Epilepsy Study (HERQULES), a ten-year longitudinal study of children, aged four to 12 years, with newly diagnosed epilepsy. Epilepsy-specific HRQOL was self-reported by AYA eight and ten years after diagnosis and by parents at multiple time points throughout the ten-year follow-up. Measures of HRQOL over time were analyzed using a linear mixed effect model approach. Parent-youth agreement was evaluated using intraclass correlation coefficient (ICC) and Bland-Altman plots. Results: A total of 165 AYAs participated at long-term follow-up. There was considerable heterogeneity among AYA’s HRQOL, and as a group there was no significant change in HRQOL from the eight- to ten-year follow-up. Household income at the time of diagnosis, seizure control at follow-up, and a history of emotional problems (anxiety/depression) were independent predictors of HRQOL at follow-up. AYA-parent agreement on AYA’s HRQOL was moderate (ICC:0.62, 95%CI 0.51–0.71), though considerable differences were observed at the individual level. AYA-parent agreement varied with AYA’s and parent’s age, seizure control, and family environment. Conclusions: In the long-term after a diagnosis of epilepsy AYAs report stable HRQOL over time at the group level, although notable individual differences exist. Seizure control, anxiety/depression, and family environment meaningfully impact AYA’s long-term HRQOL. AYA and parent reports on HRQOL are similar at the group level, though cannot be used interchangeably, given the large individual differences observed. Funding: Please list any funding that was received in support of this abstract.: Canadian Institutes of Health Research (CIHR)