Grape pomace, the solid byproduct of grape processing industry, is a potential biomass feedstock for biogas energy production through anaerobic digestion (AD). However, the lignocellulosic structure of the cell wall limits the bioconversion rate and efficiency because it reduces the accessibility of microbes and enzymes to the substrates. This study was conducted to investigate using alkaline pretreatment to increase the bioconversion efficiency of grape pomace. Sodium hydroxide was used at four different loadings of 0.02, 0.06, 0.10 and 0.14 g NaOH/g-dry substrate and two types of grape pomace were tested, including fresh and fermented pomace. The pretreatment time and temperature were 24 hours and 20 ^oC, respectively. As a comparison, high temperature pretreatment at 0.10 g NaOH/g-dry substrate and 121 ^oC for 1 hour was tested. The pretreated grape pomace without solid-liquid separation were used for biodegradability test in batch anaerobic reactors. Cumulative biogas yield, biogas production rate and methane content for each pretreatment condition were monitored. For fresh grape pomace, the highest biogas yield after 20 days of digestion among six treatments was 494 mL/g VS for 0.06 g/g loading, and 0.10 g/g with high temperature condition had the lowest biogas yield of 392 mL/g VS. For fermented grape pomace, the highest biogas yield after 20 days of digestion among six treatments was 540 mL/g VS for 0.06 g/g chemical loading at 20 ^oC, and the high temperature condition resulted in the lowest biogas yield of 440 mL/g VS. The overall methane content of biogas for all the test conditions were similar at about 70%. Economic analysis was then conducted based on the results of this study to evaluate the financial viability of NaOH pretreatment on the grape pomace for biogas energy production.