Excessive poly(ADP-ribose) polymerase-1 (PARP-1) activation plays a significant role in ischemic brain damage. Increasing evidence has supported the hypothesis that PARP-1 induces cell death by depleting intracellular NAD⁺. Based on our in vitro finding that NAD⁺ treatment can abolish PARP-1-mediated cell death, we hypothesized that NAD⁺ administration may decrease ischemic brain injury. In this study, we used a rat model of transient focal ischemia to test this hypothesis. We observed that intranasal NAD⁺ delivery significantly increased NAD⁺ contents in the brains. Intranasal delivery with 10 mg/kg NAD⁺ at 2 hours after ischemic onset profoundly decreased infarct formation when assessed either at 24 or 72 hours after ischemia. The NAD⁺ administration also significantly attenuated ischemia-induced neurological deficits. In contrast, intranasal administration with 10 mg/kg nicotinamide did not decrease ischemic brain damage. These results provide the first in vivo evidence that NAD⁺ metabolism is a new target for treating brain ischemia, and that NAD⁺ administration may be a novel strategy for decreasing brain damage in cerebral ischemia and possibly other PARP-1-associated neurological diseases.