Three experiments were conducted to investigate the effects of hesperidin supplementation on growth performance, immune function, and antioxidant activity of growing pigs (56 d old; average BW 20.4±0.6kg). In Exp. 1, 24 pigs with an initial BW of 19.53 kg were randomly allotted to three treatments, and fed for 9-wk either on a basal diet (CON), alone or with 0.01% (Hes-1), and 0.02% hesperidin (Hes2). Initial and final BW, ADG or average daily feed intake were not different among the treatments. Hes-1 or Hes-2 groups, on the other hand, had a higher (P<0.05) gain: feed ratio compared to CON group. Antioxidant activity in terms of serum superoxide dismutase activity was increased (P<0.05) in Hes-2 compared to CON group. To confirm this beneficial effect of hesperidin as an antioxidant reagent, in vitro antioxidant activities of hesperidin were ascertained vis-a-vis butylated hydroxytoluence (BHT) in Exp. 2 by using the 1, 1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging activity. Hesperidin showed lower (P<0.05) IC50(concentration for scavenging 50% of DPPH radicals) than BHT. In Exp.3, 12 barrows (13.8±0.9 kg BW) fed 0 (CON), 0.02% (Hes-0.02) or 0.04% (Hes-0.04) of hesperidin for 4-wk were challenged with lipopolysaccharide (LPS; 50 μg/kg BW). Blood samples were obtained at 0, 3, 6, 12 and 24 h to determine immune response. There was no effect of hesperidin on levels of immuneglobulins (IgM, IgG and IgA). Taken together, administration of hesperidin has beneficial effects on feed efficiency and antioxidant activity suggesting that hesperidin can be used as a feed additive in growing pigs.