Background Although the outcome of cardiopulmonary resuscitation (CPR) is still unsatisfactory, there are few studies about temporal trends of in-hospital CPR incidence and mortality. We aimed to evaluate nationwide trends of in-hospital CPR incidence and its associated risk factors and mortality in pediatric patients using a database of the Korean National Health Insurance between 2012 and 2018. Methods and Results We excluded neonates and neonatal intensive care unit admissions. Incidence of in-hospital pediatric CPR was 0.58 per 1000 admissions (3165 CPR/5 429 471 admissions), and the associated mortality was 50.4%. Change in CPR incidence according to year was not significant in an adjusted analysis (=0.234). However, CPR mortality increased significantly by 6.6% every year in an adjusted analysis (<0.001). Hospitals supporting pediatric critical care showed 37.7% lower odds of CPR incidence (<0.001) and 27.5% lower odds of mortality compared with other hospitals in the adjusted analysis (<0.001), and they did not show an increase in mortality ( for trend=0.882). Conclusions Temporal trends of in-hospital CPR mortality worsened in Korea, and the trends differed according to subgroups. Study results highlight the need for ongoing evaluation of CPR trends and for further CPR outcome improvement among hospitalized children.