Aim: We aimed to investigate the prognostic performance between serum NSE and cerebrospinal fluid (CSF) NSE for 6-month neurologic outcome in OHCA survivors underwent target temperature management (TTM). Hypothesis: We hypothesized that the NSE levels measured in the CSF would affect the change, earlier and more sensitively than serum, according to severity of hypoxic brain damage. Methods: This single-centre prospective observational study included out-of-hospital cardiac arrest (OHCA) patients underwent TTM. NSE levels were assessed in blood and CSF samples obtained immediately (Day 0), and 24 h (Day 1), 48 h (Day 2), and 72 h (Day 3) after return of spontaneous circulation (ROSC). The primary outcome was the 6-month neurological outcome. Results: We enrolled 34 patients (males, 24; 70.6%), 16 (47.1%) had a poor neurologic outcome. CSF NSE and serum NSE values were significantly higher in the poor outcome group compared to the good outcome group at each time point, except for serum Day 0. CSF NSE and serum NSE had area under curve (AUC) of 0.819-0.972 and 0.648-0.920, respectively. CSF NSE prognostic performances were significant higher than serum NSE at Day 1 and showed excellent AUC values (0.969; 95% Confidential Interval [CI] 0.844-0.999) and high sensitivity (93.8%; 95% CI 69.8-99.8) at 100% specificity. Conclusion: We found CSF NSE values were highly predictive and sensitive markers of 6-month poor neurological outcome in OHCA survivors treated with TTM at Day 1 after ROSC. Thus, CSF NSE level at day 1 after ROSC can be a useful early prognosticator in OHCA survivors.