To assess incidence rates of clinically diagnosed eating disorders among Danish youth before, during, and after the COVID-19 pandemic. This study used a population-based time series analysis with individual-level data from Danish healthcare registries. Participants included all Danish individuals aged 6-24 years from January 1, 2015, to December 31, 2023. Monthly incident cases of any eating disorder, anorexia nervosa, and bulimia nervosa were analyzed using interrupted time-series analysis. We estimated the cumulative number of excess cases of incident eating disorder diagnoses and risk ratios (RR) associated with the pandemic and post-pandemic periods compared with pre-pandemic predictions. The study population encountered a mean of 1,310,542 individuals during the study period. The study included 11,693 individuals diagnosed with an eating disorder, median age 17 (IQR 14-20 years). Incident cases increased during the pandemic (RR 1.29, 95% CI 1.15-1.45) and normalized post-pandemic (RR 1.07, 95% CI 0.91-1.25) compared with pre-pandemic predictions. Similar patterns were seen for anorexia and bulimia. Increases were significant for ages 13-16 (RR 1.19, 95% CI 1.02-1.38), 17-19 (RR 1.51, 95% CI 1.25-1.83), and 20-24 (RR 1.35, 95% CI 1.12-1.64). Post-pandemically, a continued increase was observed only for ages 20-24 (RR 1.32, 95% CI 1.02-1.71). The study documents a temporary increase in diagnosed eating disorders among Danish youths during the COVID-19 pandemic, with rates later returning to pre-pandemic levels. These results provide insights into the pandemic's impact on adolescents and youths.