Lycium barbarum polysaccharides (LBP) are considered to be the major bioactive components of L. barbarum and have been widely used as a well-known traditional Chinese medicine and functional food because of their various biological activities. However, no published research has investigated the use of LBP as a feed additive in broilers. The objective of this study was to evaluate the effects of dietary LBP supplementation on the growth performance, digestive enzyme activities, antioxidant status, and immunity of broiler chickens. A total of 256 one-day-old Arbor Acres male broiler chicks were randomly allotted into 4 groups, with 8 replicates of 8 birds each, and were fed a corn–soybean meal–type basal diet supplemented without (control group) or with 1,000, 2,000, or 4,000 mg/kg LBP for 6 wk. The results showed that compared with the control diet, a significant increase in ADG (P < 0.05) during the grower and overall periods was observed in chickens fed the basal diet supplemented with 2,000 mg/kg LBP, whereas supplementation with 1,000 or 2,000 mg/kg LBP decreased feed-to-gain ratio (P < 0.05) during the starter period. The inclusion of LBP in the broiler diets increased overall amylase, lipase, and protease activities (P < 0.05). Supplementation with increasing levels of dietary LBP increased the activities of superoxide dismutase and glutathione peroxidase but decreased malondialdehyde content in the serum and liver (P < 0.05). Broilers fed with LBP-containing diets exhibited higher serum IgG and IgA concentrations (P < 0.05) than the broilers fed with the control diet. Serum tumor necrosis factor α and IL-4 concentrations were significantly elevated in the group fed 2,000 mg/kg LBP compared with the control group (P < 0.05). Broilers fed diets supplemented with LBP showed linear (P < 0.05) and quadratic (P < 0.05) increases in serum IL-6 and interferon gamma concentrations. The results indicated that dietary LBP supplementation can improve growth performance, digestive enzyme activities, antioxidant capacity, and immune function of broilers. In conclusion, LBP may be used as a promising feed additive for broilers, and a supplementation level of 2,000 mg/kg LBP in the broiler diet is recommended.