Epidemiological studies support the association between inadequate vitamin C (Vc) intake and non-alcoholic fatty liver disease (NAFLD). However, the intervention dose of Vc, and the prophylactic and therapeutic effects on NAFLD are unclear. This study aimed to investigate the prophylactic and therapeutic effects of low (LVc), medium (MVc) and high (HVc) doses of Vc on NAFLD. C57BL/6 mice were randomly assigned to prophylactic groups (mice received a high-fat diet (HFD) concomitant with different doses of Vc) and therapeutic groups (HFD-induced NAFLD mice treated with different doses of Vc). Results showed that prophylactic LVc and MVc administration reduced the risk of NAFLD development in HFD-fed mice, as evidenced by significantly lowered body weight, perirenal adipose tissue mass, and steatosis, whereas prophylactic HVc administration did not prevent HFD-induced NAFLD development. Furthermore, therapeutic MVc administration significantly ameliorated HFD-induced increase in body weight, perirenal adipose tissue mass and steatosis, whereas therapeutic LVc and HVc administration did not ameliorate NAFLD symptoms. In fact, therapeutic HVc administration significantly increased body weight, perirenal adipose tissue mass, and lobular inflammation. Moreover, prophylactic LVc administration was more effective than therapeutic LVc administration as evidenced by significantly lower body weight, perirenal adipose tissue mass, steatosis, ballooned hepatocytes, and lobular inflammation in prophylactic LVc administration. The same trends were observed between prophylactic HVc administration and therapeutic HVc administration. In addition, all Vc-administered mice exhibited low blood glucose, triglycerides and homeostasis model assessment of insulin resistance values and high adiponectin levels compared to HFD-fed mice. Our study suggested that MVc was beneficial for HFD-induced NAFLD prophylaxis and therapy. LVc prevented HFD-induced NAFLD development, while HVc for NAFLD management was risky. This study offers valuable insight into the effect of various Vc doses on NAFLD management.