Pitaya is a rich source of bioactive compounds, such as polyphenols and betalains. Moreover, these compounds has been associated with reduced risk of type 2 diabetes mellitus. The aim of this study is to evaluate the effect of this fruit on glycemia and oxidative stress in aloxan-induced diabetic mice. Thus, considering that In the in vivo assays, the mice were divided into 5 groups (n = 6): (a) healthy group treated with water; (b) diabetic mice treated with metformin at 200 mg/kg body weight diluted in water; (c) untreated diabetic mice; (d) diabetic mice treated with pitaya at 200 mg/kg and (e) diabetic mice treated with pitaya at 400 mg/kg of body weight diluted in water. The results shows that pitaya was able significantly to reduce blood glucose (p < 0.05) (200 mg/kg); significantly reduce cholesterol (200 and 400 mg/kg) and significantly increase HDL-c (400 mg/kg) levels. In the oxidative stress experiment, Malondialdehyde levels in the liver were significantly reduced (p < 0.05) in the groups treated with pitaya, when compared to the other groups, suggesting lower lipid peroxidation. The consumption of pitaya reduced the blood glucose and cholesterol and increase the HDL, in addition, the lipid peroxidation -which is common in diabetic patients, was reduced.