Biodiesel is a bio-renewable fuel derived from vegetable oils and animal fats with less environmental pollution than fossil fuels. This research aims to design, fabricate, and evaluate a hydrodynamic reactor for biodiesel production. According to the fluid characteristic, the rotor and stator were designed and the electric engine was chosen. The cavities of the rotor were designed for optimal cavitation. The effect of reaction time and rotational speed were examined to assess the reactor. Speed rotor rotational speed of hydrodynamic cavitation reactors can intensify the transesterification reaction by increasing the occurrence of cavitation in the space between the rotor and the stator. Therefore, to investigate the effect of this variable on biodiesel production efficiency, three levels were selected (2000, 2500, and 3000 rpm). As the rotational speed of the hydrodynamic reactor increases, the cavitation operation increases, and as a result, the conversion percentage rises too. This experiment indicated that the rise of residence time from 30 s to 60 s increases methyl esters yield, but following the time up to 60 s, the methyl esters yield has no significant changes. The results showed that the biodiesel produced from waste oil in the hydrodynamic reactor could be a suitable alternative to diesel. تفاصيل المقالة