The objective of this study was to evaluate the effects of dietary supplementation with different levels of nano-selenium (NS) on growth performance, antioxidant activity, biochemical parameters, and selenium content in Landes geese. A total of 120 80-week-old healthy Landes geese (4.44±0.03 kg) were randomly assigned to three groups, each with four replicates of 10 birds. The control birds were fed a basal diet without further dietary supplementation (0.0 mg/kg of NS) and the two experimental groups were fed the basal diet supplemented with dietary NS at 0.2 or 0.4 mg/kg of feed. The results demonstrated that NS dietary supplementation had no significant effect on growth performance. Increased total superoxide dismutase activity in serum, breast muscle and liver, glutathione peroxidase level in serum and liver, and catalase in breast muscle and liver were observed for both NS supplemented groups. Additionally, reduced malondialdehyde in serum, breast muscle, and liver was detected in both NS-supplemented groups. Compared with the control, the birds fed diets supplemented with NS had lower concentrations of alanine aminotransferase, triglyceride, aspartate aminotransferase, and low-density lipoprotein cholesterol in serum, while high-density lipoprotein cholesterol was increased. Furthermore, increased selenium, especially in the liver, was found in groups with dietary supplementation of NS. These findings suggest the supplementation of NS in diets can improve antioxidant status, biochemical parameters, and tissue selenium content, although it has no significant effect on growth performance of Landes geese.