Background: Early prediction of neurologic outcome is important to patients treated with therapeutic hypothermia after hypoxic brain injury. Hypoxic brain injury patients may have poor neurologic prognosis due to increased intracranial pressure. Increased intracranial pressure can be detected by optic nerve sheath diameter (ONSD) measurement in computed tomography (CT) or ultrasound. In this study, we evaluate the relation between neurologic prognosis and optic nerve sheath diameter measured in brain CT of hypoxic brain injury patients. Methods: We analyzed the patient clinical data by retrospective chart review. We measured the ONSD in initial brain CT. We also measured and calculated the gray white matter ratio (GWR) in CT scan. We split the patients into two groups based on neurologic outcome, and clinical data, ONSD, and GWR were compared in the two groups. Results: Twenty-four patients were included in this study (age: 52.6 ± 18.3, 18 males). The mean ONSD of the poor neurologic outcome group was larger than that of the good neurologic outcome group (6.07 mm vs. 5.39 mm, p = 0.003). The GWR of the good neurologic outcome group was larger than that of the poor outcome group (1.09 vs. 1.28, p = 0.000). ONSD was a good predictor of neurologic outcome (area under curve: 0.848), and an ONSD cut off ≥ 5.575 mm had a sensitivity of 86.7% and a specificity of 77.8%. Conclusions: ONSD measured on the initial brain CT scan can predict the neurologic prognosis in cardiac arrest and hanging patients treated with therapeutic hypothermia.