Optic nerve sheath diameter (ONSD) can help predict the neurologic outcome of patients with post-cardiac arrest (CA) return of spontaneous circulation (ROSC). We aimed to investigate the effect of ONSD changes before and after CA on neurologic outcomes in patients with ROSC after CA using brain computed tomography (CT). The study included patients hospitalized after CA, who had undergone pre- and post-CA brain CT from January 2001 to September 2020. The patients were divided into good and poor neurologic outcome (GNO and PNO, respectively) groups based on the neurologic outcome at hospital discharge. We performed between-group comparisons of the amount and rate of ONSD changes on brain CT and calculated the area under the curve (AUC) to determine their predictive value for neurologic outcomes. Among the 96 enrolled patients, 25 had GNO. Compared to the GNO group, the PNO group showed significantly higher amount (0.30 vs. 0.63 mm; p=0.030) and rate of change (5.26 vs. 12.29 %; p=0.041). The AUC for predicting PNO was 0.64 (95% CI=0.53–0.73; p=0.04) and patients with a rate of ONSD change >27.2% had PNO with 100% specificity and positive predictive value. Hence, ONSD changes may predict neurologic outcomes in patients with post-CA ROSC.