This study evaluated the efficacy of fermented corn (FC) in growing pigs. One hundred twenty-eight growing pigs [(Landrace × Yorkshire) × Duroc)] with an initial body weight of 29.59 ± 1.34 kg were used in a 6 wk experiment. Pigs were assigned into one of four dietary treatments in a 2 × 2 factorial arrangement with two levels of nutrient density (high energy: 3.37 Mcal kg^-1, or low energy: 3.29 Mcal kg^-1) and FC (0% or 20% substitute for corn). Pigs fed diets with FC increased (P < 0.05) average daily gain (ADG) overall. Pigs fed with high-density (HD) diets increased (P < 0.05) ADG and gain to feed (G/F) ratio overall. Apparent total tract digestibility (ATTD) of dry matter (DM), gross energy (GE), and nitrogen (N) increased (P < 0.05) in pigs fed with FC diets compared with pigs fed the diets without FC. In addition, pigs fed with HD diets increased (P < 0.05) ATTD of DM and GE compared with low-density (LD) diets. Furthermore, pigs fed with HD diets had a higher (P < 0.05) ATTD of DM and GE than those fed with LD diets. Both LD and FC supplementation led to lower (P < 0.05) fecal gas emission content. Pigs fed FC diets increased ileal Lactobacillus concentration and decreased Escherichia coli concentration. An interactive effect between nutrient density diet and FC was observed on the G/F, Lactobacillus on ileal microorganisms, and nutrient digestibility. In conclusion, the results indicated that dietary supplementation of HD diets and FC improved performance in growing pigs.