Objectives were to evaluate the effects of de-oiled wet distillers bran plus solubles (WDBS) as a protein source [when included at 150 g/kg of diet dry matter (DM)] to replace soybean meal (SBM); or as a protein and energy source (when included at 300 and 450 g/kg of diet DM) to replace a mix of soybean meal, ground flint corn, and citrus pulp, and to evaluate the effects of corn oil inclusion (0vs 30 g/kg of diet DM) in diets containing 0 to 450 g/kg of WDBS (DM basis). Two hundred and thirty-two Nellore bulls (BW = 425 ± 25 kg) were used in a randomized complete block design with a 2 × 4 factorial arrangement of treatments consisting of diets supplemented or not with 30 g/kg of corn oil (DM basis) each one combined with 4 inclusions of WDBS (0, 150, 300, and 450 g/kg; DM basis). Bulls were blocked by initial shrunk BW and allocated into 40 pens (5 pens/treatment; 5 or 6 bulls/pen). Effects of corn oil × WDBS interaction were not detected (P ≥ 0.29) for feedlot growth performance, carcass traits, and dietary NE concentrations, except for dry matter intake (DMI; P = 0.03). Increasing inclusion of WDBS linearly decreased DMI (P = 0.004) of finishing bulls fed diets without corn oil supplementation, but quadratically decreased DMI (P = 0.002) in diets containing 30 g/kg of corn oil, resulting in the observed interaction (P = 0.03). Feeding WDBS did not affect average daily gain (ADG), hot carcass weight (HCW), and dressing percentage of finishing bulls regardless of corn oil supplementation (P ≥ 0.18). Feed efficiency (G:F) tended (linear; P = 0.09) to increase due to WDBS inclusion. The inclusion of 30 g/kg corn oil (DM basis) in the diet tended (P = 0.07) to decrease DMI by 3% and increase G:F by 7.5% compared with diets not supplemented with corn oil. Including 30 g/kg of corn oil (DM basis) in the diet increased (P = 0.05) observed net energy of maintenance (NEm) and net energy of gain (NEg). Corn oil supplementation had no effect (P ≥ 0.19) on final BW, ADG, HCW, and dressing percentage. In summary, WDBS is as a protein supplement alternative to SBM when fed at 150 g/kg of the diet DM. The supplementation with corn oil is an effective way to increase the energy density of finishing diets containing WDBS.