Abstract Purpose A recent study showed that increased blood glucose variability was an independent predictor of mortality in cardiac arrest survivors treated with therapeutic hypothermia (TH). We hypothesized that the association of blood glucose variability with outcomes would differ depending on the TH phase, as body temperature affects glucose homeostasis. Methods A retrospective cohort of 147 consecutive cardiac arrest patients treated with TH was analyzed. Mean absolute glucose change (MAGC) was calculated using blood glucose values during the entire TH period and during each TH phase (induction, from the TH initiation to the achievement of the target temperature; maintenance, 24 hours from the end of induction; and rewarming, from the end of the maintenance to the achievement of 36.5°C). The primary and secondary outcomes were mortality and neurological outcome at 30 days. Multivariate regression analyses were performed with variables with a significance level <0.1 on univariate analyses. Results The hypoglycemia rate increased significantly during the rewarming phase compared with the maintenance phase (P = .003). The MAGC during the TH maintenance phase was an independent predictor of mortality (OR = 1.056, 95% CI 1.008-1.107, P = .023) and unfavorable neurologic outcome (OR = 1.202, 95% CI 1.043-1.384, P = .038), while the MAGC during the rewarming phase and the entire TH period were not. Conclusion The increased MAGC during the TH maintenance phase was associated with mortality and unfavorable neurologic outcome. However, this study cannot prove a causal association due to the retrospective design. In addition, we showed that the hypoglycemia rate increased significantly during the rewarming phase.