BACKGROUND: A better understanding of the epidemiology of pediatric out-of-hospital cardiac arrest (OHCA) occurring in nursery schools and kindergartens is indispensable to establish an evidence-based strategy for prevention and improved outcomes. This study aimed to describe the incidence, characteristics, and outcomes of pediatric OHCAs that occurred in certified nursery schools and kindergartens. METHODS: Stop and Prevent cardIac aRrest, Injury, and Trauma in Schools (SPIRITS) is a study to construct and analyze a nationwide registry of pediatric OHCAs occurring in school settings in Japan. Using data from the SPIRITS registry, we assessed the incidence, characteristics, and outcomes of pediatric OHCAs that occurred in certified nursery schools/kindergartens between April 2008 and December 2016. RESULTS: During the study period, 37 OHCA patients (31 in certified nursery schools and 6 in kindergartens) were confirmed. The overall incidence rate was 0.13 per 100,000 children per year. Among 37 patients, 57% (21/37) had an OHCA while napping and 35% (13/37) experienced OHCA that was witnessed by bystanders. Although public-access automated external defibrillator pads were applied by bystanders in 24% (9/37) of cases, only 1 patient actually received defibrillation. Overall, the proportion of 1-month survival with favorable neurological outcomes after OHCA was 19% (7/37). Among those with OHCA of non-medical origins, 60% (3/5) of patients experienced arrest caused by suffocation, 60% (3/5) by drowning, and 100% (1/1) by head injury. In contrast, no patient had 1-month favorable neurological outcomes among those with OHCA of medical origins such as presumed cardiac origin (0/17), sudden infant death syndrome (0/6), acute viral myocarditis (0/1), respiratory disease (0/1), and ventricular fibrillation (0/1). CONCLUSIONS: In this population, the majority of pediatric OHCAs occurring in certified nursery schools/kindergartens had non-ventricular fibrillation rhythm, and their outcomes after OHCA of medical origin were poor.