Cardiopulmonary resuscitation (CPR) education for schoolchildren is emphasized, as bystander CPR is a vital key to increasing the survival rate of out-of-hospital cardiac arrest (OHCA) victims. This study was conducted to verify the effect of CPR education on knowledge, attitudes, self-efficacy, and confidence of Korean elementary school students in performing CPR. Data were collected through structured questionnaires before and after CPR education and analyzed using descriptive statistics, T-tests, and hierarchical regression. Significant improvements in CPR knowledge, attitudes, self-efficacy, and confidence in performing CPR were found after CPR education, with the greatest increase observed in confidence (p = 0.000). The influencing factors on confidence in performing CPR were school grade, attitude, and self-efficacy. Although a significant increase in schoolchildren's CPR knowledge after education was shown, knowledge did not affect confidence in performing CPR. Therefore, early CPR education which focuses on improving confidence in performing CPR is recommended. CPR education might raise attitude and self-efficacy leading to increased confidence in performing bystander CPR. In conclusion, early and regular CPR education for elementary school students is crucial and should be conducted repeatedly.