BACKGROUND: The aim of this study was to investigate the relationships between left ventricular ejection fraction (LVEF) and mortality and neurologic outcomes with post-cardiac arrest syndrome (PCAS) after out-of-hospital cardiac arrest (OHCA). METHODS: Patients with PCAS after OHCA admitted to the intensive care unit between January 2014 and December 2015 were analyzed retrospectively. RESULTS: total of 104 patients were enrolled in this study. The mean age was 54.4 ± 15.3 years, and 75 of the patients were male (72.1%). Arrest with a cardiac origin was found in 55 (52.9%). LVEF < 45%, 45-55%, and > 55% was measured in 39 (37.5%), 18 (17.3%), and 47 (45.2%) of patients, respectively. In multivariate analysis, severe LV dysfunction (LVEF < 45%) was significantly related to 7-day mortality (odds ratio 3.02, 95% Confidence Interval 1.01-9.0, p-value 0.047). CONCLUSIONS: In this study, moderate to severe LVEF within 48 hours after return of spontaneous circulation was significantly related to 7-day short-term mortality in patients with PCAS after OHCA. Clinicians should actively treat myocardial dysfunction, and further studies are needed.