Pretreatment of the empty fruit brunch (EFB) from oil palm was investigated for H-2 fermentation. The EFB was hydrolyzed at various temperatures, H2SO4 concentrations, and reaction times. Subsequently, the acid-hydrolysate underwent enzymatic saccharification under various temperature, pH, and enzymatic loading conditions. Response surface methodology derived the optimum sugar concentration (SC), hydrogen production rate (HPR), and hydrogen yield (HY) as 28.30 g L-1, 2601.24 mL H-2 L(-1)d(-1), and 275.75 mL H-2 g(-1) total sugar (TS), respectively, at 120 degrees C, 60 min of reaction, and 6 vol% H2SO4, with the combined severity factor of 1.75. Enzymatic hydrolysis enhanced the SC, HY, and HPR to 34.52 g L-1, 283.91 mL H-2 g(-1) TS, and 3266.86 mL H-2 L(-1)d(-1), respectively, at 45 degrees C, pH 5.0, and 1.17 mg enzyme mL(-1). Dilute acid hydrolysis would be a viable pretreatment for bio-hydrogen production from EFB. Subsequent enzymatic hydrolysis can be performed if enhanced HPR is required. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.