A safe, convenient, and environmentally benign laboratory experiment for the synthesis of biodiesel from six kinds of vegetable oils has been developed for the introductory organic chemistry laboratory. The experiment uses ultrasonic irradiation in the presence of a base catalyst at room temperature and atmospheric pressure. Because of safer and greener conditions, shorter reaction time and separation time, high purity (close to 100%) and high yields, and lower generation of waste or pollutants, this experiment is a good example to introduce students to the Twelve Principles of Green Chemistry as well as important organic chemistry concepts and techniques. Moreover, a low-cost ultrasonic cleaner is used as the ultrasonic irradiation source in the experiment, which allows the project to be widely implemented in high-school- and college-level laboratory curricula.