It is thought that vitamin C has protective roles on stress-induced heart damage and the development of cardiovascular diseases, but its precise role and mechanisms are unclear. In the present study, we investigated the specific mechanisms by which vitamin C leads to protecting the heart from stress-induced damage in the Gulo(-/-) mice which cannot synthesize vitamin C like humans. By exposure to stress (1 h/day), the heartbeat and cardiac output in vitamin C-insufficient Gulo(-/-) mice were definitely decreased, despite a significant increase of adrenaline (ADR) and noradrenaline (NA) production. A change of cardiac structure caused by the death of cardiomyocytes and an increased expression of matrix metalloprotease (MMP)-2 and -9 were also found. Moreover, lipid peroxidation and the production of tumor necrosis factor-alpha (TNF-α) in the heart were increased. Finally, all vitamin C-insufficient Gulo(-/-) mice were expired within 2 weeks. Interestingly, all of the findings in vitamin C-insufficient Gulo(-/-) mice were completely prevented by the supplementation of a sufficient amount of vitamin C. Taken together, vitamin C insufficiency increases the risk of stress-induced cardiac damage with structural and functional changes arising from the apoptosis of cardiomyocytes.