Biodiesel, an alternative diesel fuel, is made from renewable biological sources such as vegetable oil, waste cooking oil, and animal fat. This work for the first time presents the biodiesel production from Tra fat with methanol using KOH/γ-Al₂O₃ catalyst as heterogeneous catalyst using low frequency ultrasonic mixing (20 kHz). The main object of this study was to investigate the influences of parameters like methanol/fat molar ratio, catalyst concentration, time and temperature of reaction, wave amplitudes, and energy input on the yield of biodiesel. Moreover, this research also examined the influences of ultrasonic wave on the fatty acid composition and the properties of KOH/γ-Al₂O₃ catalyst. [DOI: 10.1380/ejssnt.2011.477]