This study investigated the effects of feeding dairy cows regular (RCS) or brown midrib corn silage (BMCS) based diets on enteric CH₄ emissions. In a crossover design (35-d periods), 16 lactating multiparous Holstein cows (BW = 691 ± 77 kg; DIM = 119 ± 27; milk yield = 43.5 ± 6.4 kg/d) were fed (ad libitum; 5% orts on as-fed basis) a TMR (65:35 forage:concentrate ratio) containing 59% (dry matter basis) RCS or BMCS. Production of CH₄ was measured (3 consecutive days) using respiration chambers. Rumen fermentation characteristics were assessed over 2 consecutive days, and milk performance and nutrient apparent-total-tract digestibility were determined over 6 consecutive days. Effects of dietary corn silage cultivar were determined using the MIXED Procedure of SAS and significance was declared at P ≤ 0.05. Compared with feeding RCS, feeding BMCS increased (P ≤ 0.01) dry matter intake (+ 1.6 kg/d), milk yield (+ 3.2 kg/d) without affecting milk fat (3.87% ± 0.11) and milk protein (3.50% ± 0.05) contents. Dietary treatment did not affect ruminal pH, protozoa numbers, volatile fatty acid profile and apparent total-tract digestibility of organic matter, including its fiber fraction. Daily enteric methane emission averaged 476 g/d (±21) and was not affected by dietary treatment. Methane energy losses (proportional to gross energy intake) were 7% lower (P = 0.05) in cows fed BMCS (5.16%) compared with cows fed RCS (5.52%). Similarly, CH₄ emitted per kg of milk was lower (P = 0.02) in cows fed BMCS (12.7 g/kg) than in cows fed RCS (14.3 g/kg). It is concluded that replacing RCS with BMCS in dairy cow diets has the potential to lower CH₄ production per unit of energy consumed or unit of milk produced. Possible influence of feeding RCS or BMCS-based diets on gaseous emissions from manure needs to be evaluated.