1. The effects of nutrient density and lighting regime on oxidant status and immune function of broilers were investigated in a 2 x 4 experimental design (8 groups of 576 chickens). 2. There were two nutrient densities: high (H) starter diet AME 13.39 MJ/kg, 230 g crude protein (CP)/kg: finisher 13.39 MJ/kg, 197 g CP/kg CP) and low (L) starter AME 12.03 MJ/kg, 208 g CP/k; finisher 12.14 MJ/kg, 183 g CP/kg C. The 4 lighting regimes were continuous (CL) 23L:1D, 20L:4D (12L:2D:8L:2D), 16L:8D (12L:3D:2L:3D:2L:2D) and 12L:12D (9L:3D:1L:3D:1L:3D:1L:3D). Blood and lymphoid organs were collected at d 21 and 42 for assay of antioxidant indices and immunity. 3. Chickens fed low density diet had a higher Fabricius bursa weight (FBW). Low density diet tended (P = 0.089) to increase the a-Naphthylacetate esterase (ANAE) positive percentage response at 42 d. 4. The 12L:12D schedule decreased serum malondialdehyde compared with other regimes at 21 d. At 42 d, it was lower in the 12L:12D and 16L:8D groups than in CL and 20L:4D. There was a trend (P = 0.086) for greater superoxide dismutase activity in the 12L:12D and 16L:8D groups than under the CL and 20L:4D regimes at 42 d. ANAE positive percentage in 12L:12D group at 42 d was higher than in CL and 20L:4D groups. Plasma IgG in the 12L:12D group at 42 d was higher than in the CL group. 5. There was an interaction between nutrient density and lighting regime for FBW at 42 d. 6. These results demonstrate that low nutrient density and a 12L:12D schedule lighting schedule can enhance oxidant-antioxidant balance and the immune functions of broilers.