Mild hypothermia is a robust neuroprotective treatment for stroke. Understanding the mechanisms underlying hypothermia's benefits will lead to more effective treatments to prevent stroke damage. Delta protein kinase C (dPKC) is a kinase that has been strongly implicated in executing ischemic damage. We investigated the effects of hypothermia on dPKC activation, as determined by its subcellular translocation, proteolytic cleavage, and phosphorylation in a focal cerebral ischemia model. The amount of constitutively activated C-terminal catalytic fragment of dPKC (CF-dPKC) increased after stroke. Both hypothermia (301C) and the caspase-3-specific inhibitor, Z-DQMD-FMK, blocked the accumulation of activated dPKC in the penumbra. Other hallmarks of dPKC activation, its translocation to the mitochondria, and nucleus were observed in the penumbra as early as 10 mins after reperfusion. These events were blocked by hypothermia. Hypothermia also blocked CF-dPKC increases in the mitochondria and nuclei. Conversely, a specific dPKC activator, wdRACK, decreased the neuroprotective effect of hypothermia. Finally, dPKC activity may lead to mitochondrial injury and cytochrome c release, as the timing of cytochrome c release corresponded to the time course of dPKC translocation. Both cytochrome c release and dPKC translocation were blocked by hypothermia. In conclusion, hypothermia protects against ischemic damage in part by suppressing dPKC activation after stroke.