Biogas production is one of the eco-friendly strategies for energy production. Worldwide the concern about using fossil fuels and its adverse impact on the environment is increasing. Date palm leaves (P. dactylifera) are one of the major agricultural wastes produced in Oman. In this study, biogas was produced using anaerobic digestion of date palm leaves at 37 ℃ using cow dung as an inoculum with different concentrations such as 10%, 20%, 30%, 40% and 50%. The results in GC-TCD showed higher CH4 concentration in 50% inoculum digester. The substrate was then subjected to various pretreatments, including H2 SO4 2% at 100 ℃ for 43 min, NaOH 4% at 37 ℃ for 5 days and cellulase enzyme 140 units. GC- FID was used to measure CH4% and the results showed higher values in acidic and alkaline conditions, with a maximum value of 98.94% and 98.35% respectively. The concentration of VFAs was also measured during the incubation period and it showed that acetic acid is highly contracted as it reaches 38 mM after 20 days in the cellulase pretreated digester. Filter paper assay was used to measure total cellulase produced from day 5 to day 20. There is a gradual decrease in the concentration over time in the NaOH pretreated digester. Cellulase content was 0.213 FPU/ml/min on day 5 and decreased to 0.175 FPU/ml/min on day 20. Anaerobic digestion is a particularly promising alternative for the treatment of agricultural waste, as it reduces pollutants and allows for more efficient energy production.