Ketone bodies have been shown to be favorable alternative metabolic substrates and are protective under neuropathologies. At the same time, cytochrome c release has been reported following traumatic brain injury (TBI) and precipitates apoptosis via the mitochondrial pathway. The present study investigated the effects of a ketogenic diet (KD) on TBI. TBI was produced using the Feeney weight-drop model and the animals were fed either normal diet (ND) or KD. Brain edema was estimated by wet/dry weight ratio; cytochrome c was detected by Western blotting; cellular apoptosis in the penumbra area was examined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and active caspase-3 immunohistochemical staining. The results show that brain edema, cytochrome c release, and cellular apoptosis were induced after TBI and that KD reduced these changes dramatically. These findings suggest that KD has potential therapeutic benefit in TBI.