Ultrasound-assisted transesterification of palm oil by SrO/Al2O3 catalyst was investigated. Effects reaction time (10-50 min), alcohol to oil molar ratio (3:1-15:1), catalyst loading (0.5-2.5 wt%) and ultrasonic amplitude (15-95%) were studied. Response surface methodology was employed to evaluate and optimize the process. Interactions among the variables and the response were elucidated. The model was accurate with less than 5% error. 80.2% of biodiesel yield was achieved at a methanol to oil ratio of 9.2, 1.6 wt% of catalyst, 30.2 min of reaction time, and 69.7% of ultrasonic amplitude power.