Background: Astronauts will be exposed to both chronic space radiation and acute high doses of energetic radiation of solar particle events in long-term deep space missions. The application of radioprotectors in space missions has basic limitations such as their very short time window as well as their acute toxicity and considerable side effects. The aim of the present study was to investigate the potential radiation mitigation effect of vitamin C that is known as an effective antioxidant and free radical scavenger. Materials and Methods: One hundred twenty male Wistar albino rats weighing 250-300 g were randomized into the following study groups: I, control II, Only exposure to gamma-radiation (LD50/30) treated with a single dose of vitamin C, III, 1h before irradiation, IV, V and VI, 1h, 12h and 24 h after irradiation. Measurement of cell viability and proliferation was also performed by using MTT cell proliferation assay. Results: The survival rate in animals received vitamin C 1h, 12h and 24h after irradiation were 55%, 60%, and 80%, respectively. The viability of cells in animals received vitamin C 1h, 12h and 24h after irradiation were 94.9%, 99.0%, and 100%, respectively. The viability of the cells in animals only exposed to gamma rays was 50.1%. Conclusion: These findings reveal that a single dose of vitamin C can potentially be used up to 24 hours after exposure to reduce the detrimental effects of high levels of ionizing radiation in cases such as the occurrence of currently unpredictable solar particle events.