Display omitted •Experimental and numerical study of biodiesel synthesis in microdevices.•The influence of temperature, ethanol/oil ratio and catalyst concentration.•Microreactors are a viable option to produce biodiesel.•Yield parameters and selectivity better capture the experimental process. The transesterification of vegetable oils with alcohols is the most widely used method in biodiesel synthesis, generally taking place in batch processes. However, this production is currently being explored in microdevices, due to its short residence times and high conversions. This paper presents an experimental and numerical study of biodiesel synthesis in a microdevice from sunflower oil and ethanol using sodium hydroxide as catalyst. The influence of three operating variables were studied (temperature, ethanol/oil ratio and catalyst concentration). This paper also compares the reaction performance of a batch reactor with a microdevice reactor. The highest percentages of biodiesel found for the batch process and for the microdevice were 94.1% and 95.8%, respectively. These results proved the efficiency of microdevice in the biodiesel synthesis over conventional reactors. The superior results predicted for oil conversion, production yield and esters selectivity in numerical simulations were 99.90%, 2.10 and 0.42, respectively. The transesterification process simulation and intensification can be performed numerically evaluating reaction yield and selectivity parameters.