The impacts of dietary levels of oxidized vegetable (sunflower) oil on growth performance, gut morphology, nutrients utilization, serum cholesterol and meat fatty acid profile were evaluated in Ross 308 straight-run (n = 192) day-old broilers. The broilers were arbitrarily distributed among four dietary treatments including; FVO: fresh vegetable oil (1 mEq kg⁻¹), LOO: low oxidized (20 mEq kg⁻¹), MOO: moderately oxidized (40 mEq kg⁻¹), and HOO: highly oxidized vegetable oil (60 mEq kg⁻¹) with 5% inclusion containing six replicates. Results revealed that the broilers consuming MOO and HOO based diets showed reduced (p = 0.05) feed intake, body weight gain and carcass weight accompanied by a poorer feed conversion ratio than those consuming FVO. Villus height, villus height to crypt depth ratio, ileal digestibility of crude protein (p = 0.041), crude fat (p = 0.032) and poly unsaturated fatty acids (p = 0.001) in thigh muscles were decreased, whereas crypt depth (p = 0.001), serum cholesterol levels (p = 0.023) and short chain fatty acids (p = 0.001) were increased (p < 0.001) by increasing dietary oxidation level. In conclusion, MOO and HOO exerted deleterious effects on growth, carcass weight, gut development and nutrients utilization. Low oxidized vegetable oil (20 mEq kg⁻¹), however, with minimum negative effects can be used as a cost effective energy source in poultry diets.