Studies on elderly patients with out-of-hospital cardiac arrest (OHCA) treated with mild therapeutic hypothermia (TH) are few, and the unknown effects of MIH in this population are identified as an important medical problem. The aim of this study was to examine the utilization of TH after OHCA and to investigate adverse effects and outcomes in elderly patients. A total of 932 cardiac arrest patients with OHCA and treated with TH were screened from the Korean Hypothermia Network retrospective registry. In the study, 343 elderly patients were included. We analyzed the outcomes, such as mortality and the onset complications of during TH in elderly patients. Good neurologic outcomes were defined as Cerebral Performance Category scores of 1 and 2. At hospital discharge 39 (11.4%) of patients had a good neurological outcome. The median age was 71 years old, 25 (64.1%) were males. Among a good outcome, 82.1% were cardiac cause. In hospital, 99 patients were died multi-organ failure (MOF). The adverse events was developed as follows in cooling phase; hypotension (24, 7.0%), hyperglycemia (19, 5.5%), tachycardia (12, 3.5%) and bradycardia (10, 2.9%). A long time to ROSC was associated with poor outcome in the elderly patients treated with TH. In this retrospective registry study of OHCA patients treated with TH, we found an 11.4% good outcome at hospital discharge in elderly patients. The majority of mortality was MOF. The frequency of adverse events was not higher in elderly patients.