Bentonite/zeolite-P composite (B/ZP) was synthesized by simple alkaline hydrothermal treatment at 150 degrees C for 4 h and characterized by different analytical techniques. The composite was introduced as a low-cost catalyst of enhanced physiochemical properties and catalytic activity in the transesterification of palm oil into biodiesel. The catalytic activity of B/ZP catalyst was inspected by normal stirring mixing and under ultrasonic irradiation of different powers (20-60%). The best biodiesel yield by normal stirring (96.2%) was achieved at operating conditions of 210 min as conversion time, 20:1 as a methanol-to-oil molar ratio, 5 wt% as a catalyst loading, 90 degrees C as temperature and 900 rpm as stirring speed. The conversion reaction under the ultrasonic irradiation (power 60%) gives biodiesel yield of 98.8% after 120 min as reaction time using 5 wt% as catalyst loading, 20:1 as a methanol-to-oil ratio, and 90 degrees C as temperature. The ultrasonic irradiation is of positive impacts in reducing the conversion time interval, reaction temperature, catalyst loading, and methanol-to-oil molar ratio with biodiesel yield similar to that obtained by normal stirring at its best conditions. The catalyst is of higher activities than several homogenous and heterogeneous catalysts and can be reused several times with high catalytic activity especially using an organic solvent either by normal stirring or under the ultrasonic irradiation. The physicochemical specification of the obtained biodiesel by both methods matches the requirements of STM D-6571 and EN 14214 international standards.