Digestibility, performance, and initial methane production were evaluated in growing and finishing pigs. Assay 1 was carried out in experimental facilities. Sixty pigs, 30 barrows and 30 gilts (26.07 ± 0.07 kg), were allotted randomly to treatments arranged in a 3 × 2 factorial design with three diets (control, Bacillus subtilis, and lincomycin) and two genders. In assay 2, 48 pigs (26.06 ± 3.10 kg) were maintained in commercial farm and supplemented with B. subtilis and lincomycin. Performance and initial methane production were measured. In assay 3, 12 barrows (body weight = 26.55 ± 1.25 kg) were housed in metabolism crates and fed control and B. subtilis diet to evaluate nutrient balance and energy. Gilts within experimental facility, fed control diet, had higher ADG (P < 0.05) compared with lincomycin diet, but there was no statistical difference with B. subtilis diet. Numeric variations on the first and second assays suggested some improvement on pig performance and a reduction on initial methane production when pigs were fed B. subtilis diet, compared with lincomycin diet. Protein digestibility increased (P < 0.05) with B. subtilis supplementation in the diet. Dietary supplementation with B. subtilis for growing and finishing pigs may improve performance and decrease N excretion and initial methane production.