This study investigates the recovery of fermentable sugars from durian peel using ultrasound-assisted chemical pretreatment. Durian peel, a significant waste in Malaysia, is a potential substrate for fermentable sugar production. Traditional pretreatment methods, such as acid or alkaline treatment, often require extensive solid washing and generate wastewater. The study introduces ultrasound-assisted pretreatment to reduce chemical usage and improve the efficiency of lignin destruction. The morphology and chemical composition of pretreated durian peels were analyzed using SEM, FTIR, and XRD. The results showed that ultrasound-assisted pretreatment significantly altered the structure of durian peels, leading to increased sugar yield. Specifically, the combination of ultrasound and alkaline pretreatment (UB) resulted in a higher sugar yield (376.60 ± 12.14 mg reducing sugar/g dry biomass) compared to individual chemical pretreatments (237.38 ± 3.96 mg reducing sugar/g dry biomass). Enzymatic hydrolysis of the pretreated durian peels was performed, and the reducing sugar yield was measured. The UB pretreated samples showed a higher enzymatic hydrolysis efficiency (62.46%) and a higher reducing sugar yield (376.60 ± 12.14 mg reducing sugar/g dry biomass) compared to the UA pretreated samples (99.5% and 237.38 ± 3.96 mg reducing sugar/g dry biomass, respectively). Fermentability tests using *Clostridium butyricum* JKT37 demonstrated that the UB pretreated durian peels produced 2.68 mol H₂/mol consumed sugar and a productivity of 131.56 mL/L medium/h. The study concludes that ultrasound-assisted pretreatment is an effective method to enhance the recovery of fermentable sugars from durian peel, reducing chemical usage and improving the overall process efficiency.This study investigates the recovery of fermentable sugars from durian peel using ultrasound-assisted chemical pretreatment. Durian peel, a significant waste in Malaysia, is a potential substrate for fermentable sugar production. Traditional pretreatment methods, such as acid or alkaline treatment, often require extensive solid washing and generate wastewater. The study introduces ultrasound-assisted pretreatment to reduce chemical usage and improve the efficiency of lignin destruction. The morphology and chemical composition of pretreated durian peels were analyzed using SEM, FTIR, and XRD. The results showed that ultrasound-assisted pretreatment significantly altered the structure of durian peels, leading to increased sugar yield. Specifically, the combination of ultrasound and alkaline pretreatment (UB) resulted in a higher sugar yield (376.60 ± 12.14 mg reducing sugar/g dry biomass) compared to individual chemical pretreatments (237.38 ± 3.96 mg reducing sugar/g dry biomass). Enzymatic hydrolysis of the pretreated durian peels was performed, and the reducing sugar yield was measured. The UB pretreated samples showed a higher enzymatic hydrolysis efficiency (62.46%) and a higher reducing sugar yield (376.60 ± 12.14 mg reducing sugar/g dry biomass) compared to the UA pretreated samples (99.5% and 237.38 ± 3.96 mg reducing sugar/g dry biomass, respectively). Fermentability tests using *Clostridium butyricum* JKT37 demonstrated that the UB pretreated durian peels produced 2.68 mol H₂/mol consumed sugar and a productivity of 131.56 mL/L medium/h. The study concludes that ultrasound-assisted pretreatment is an effective method to enhance the recovery of fermentable sugars from durian peel, reducing chemical usage and improving the overall process efficiency.