Feeding fat to lactating dairy cows may decrease methane production additionally relative to cellulose fermentation of hemicellulose is believed to result in less methane. However, these factors have not been studied simultaneously. Eight multiparous, lactating Jersey cows averaging 98 ± 30.8 DIM and BW of 439.3 ± 56.7 kg were used in a twice replicated 4 × 4 Latin square to determine the effects of fat and hemicellulose individually and together on energy utilization and methane production using a headbox type indirect calorimetry method. To manipulate the concentration of fat, porcine tallow was included at either 0 or 2% of the diet DM. The concentration of hemicellulose was manipulated by changing the inclusion rate of corn silage, alfalfa hay, and soybean hulls resulting in either 11.3% or 12.7% hemicellulose (DM basis). The factorial arrangement of treatments were low fat low hemicellulose (LFLH), low fat high hemicellulose (LFHH), high fat low hemicellulose (HFLH), and high fat high Hemicellulose (HFHH). Neither fat nor hemicellulose affected DMI (P ≥ 0.25) averaging 16.2 ± 1.18 kg/d across treatments. Likewise, treatments did not affect (P ≥ 0.51) milk production averaging 23.0 ± 1.72 kg/d. The inclusion of fat tended (P = 0.10) to decrease methane produced per kg of DMI from 24.8 to 22.7 ± 1.61 L/kg while hemicellulose had no effect (P = 0.37). Increasing hemicellulose increased (P = 0.01) NDF digestibility from 40.6 to 50.3 ± 2.91%. Methane per unit of digested NDF tended to decrease (P = 0.11) from 64.4 to 46.9 ± 0.70 L/kg with increasing hemicellulose while fat had no effect (P = 0.70). An interaction between hemicellulose and fat content on net energy intake was observed. Specifically, increasing hemicellulose in low fat diets tended (P = 0.08) to increase net energy intake but this was not observed in high fat diets. Results confirm methane production may be decreased with the inclusion of fat while energy intake of lactating dairy cows is improved by increasing hemicellulose in low fat diets.