Utilization of EFB to increase biogas production could be developed through co-digestion of EFB and POME. Pre-treatment of EFB (shredding, grinding, and soaking) before it is utilized as a feedstock for biogas production is important to increase the biodegradability of EFB. The evaluation of the impact of EFB utilization on biogas production should be investigated to determine the optimum process conditions for biogas production from EFB and POME. This research consists of three steps: 1) Optimization of size of EFB and ratio of EFB-POME, 2) Optimization of hydrolysis and acidification retention time, and 3) Optimization of biogas production. The research result shows that co-digestion of EFB and POME increases biogas and methane production. Compared to POME only, co-digestion using POME and EFB (shredded 10%, shredded 15%, crushed 10%, and crushed 15%) is increasing biogas production in batch systems by 54.1%, 54.1%, 45.5%, and 75.2%, respectively. The research result also shows that in a continuous system with HRT for 25 days and similar feedstock, biogas production increased by 43.3%, 41.6%, 35.6%, and 62.6%, respectively, with methane concentrations maintained at about 60%. Co-digestion of EFB-POME with 15% crushed EFB is recommended to be applied in palm oil mills to increase biogas production.