OBJECTIVE: Therapeutic hypothermia improves the prognosis of patients with poor-grade subarachnoid hemorrhage (SAH). We investigated the clinical and radiological effects of therapeutic hypothermia in patients with poor-grade SAH. METHODS: Clinical and radiological data were compared between patients who underwent mild hypothermic treatment and those who underwent treatment without hypothermia. RESULTS: Among 670 patients with SAH, 72 had poor-grade SAH. After early clipping or coiling of the aneurysm, 25 patients underwent mild hypothermia and the remaining 47 patients underwent no hypothermia. The medical complication occurrence rates were similar between the hypothermia treatment and control groups. Significantly, cerebral edema was reduced in patients in the hypothermia group (44 %) compared with those in the no-hypothermia group (9 %) (p = 0.025). The poor clinical outcome rate (modified Rankin scale score > 4) assessed at discharge (p = 1.000) and 3 months after admission (p = 0.688) was similar between the two groups. However, 1 month after admission, the mortality rate of the hypothermia group (20.0 %) was remarkably lower than that of the control group (46.8 %) (p = 0.025). Multivariate logistic regression showed the therapeutic hypothermia was the most effective treatment for decreasing the mortality (OR = 4.86, P = 0.023). CONCLUSION: Mild hypothermia treatment appears to be feasible and safe for patients with poor-grade SAH. The study supports mild hypothermia treatment and its neuroprotective effects in patients with poor-grade SAH.