This article discusses the biochemical methane potential (BMP) test of the alkali pretreated “dry leaflets of Algerian date palm (Phoenix dactylifera L.) Hmira cultivar”. The anaerobic digestion (AD) experiments are performed in 4 digesters at 37 °C for 50 days. Digesters with one liter capacity for each one and a working volume of 600 mL are prepared with 10 g volatile solids (VS) of the substrate. A 6%, 12% and 18% weight/weight (w/w) NaOH (based on substrate VS) are used for alkaline pretreatment. During the performed experiments, the CH4 volume is monitored in order to evaluate the alkaline pretreatment influences. The obtained results show that a 12% NaOH is the best concentration, with a 135 mL CH4/gVS that represents an increase of methane production to 133.55% compared to the control test. A biodegradability (BD) improvement of 48.64% through the chemical oxygen demand (COD) removal is recorded with the same concentration of 12% NaOH. The technical digestion times (T80) of 22 and 32 days are recorded for both, the 12% NaOH concentration and the control test respectively, this clearly shows a shortening of 36.78% in T80. Finally, the results obtained in this experimental study show that, based on the increase of pretreatment range of the NaOH concentration (6%, 12% and 18%) before AD of the “dry leaflets of Algerian date palm (Phoenix dactylifera L.) Hmira cultivar”, an improvement of methane yield and biodegradability in shortening digestion time were registered.