In this work, the ultraviolet spectroscopy was used as a tool to monitor the kinetics of acetalization reaction of furfural with alkyl alcohols. Among the Bronsted acids evaluated, Keggin heteropolyacids (e.g., H3PW12O40 and H3PMo12O40) were the more active and selective in the acetalization of furfural in reactions carried out at room temperature. The ultraviolet spectroscopy, a simple and inexpensive analytic technique was used to quantify the furfural and acetals during the reaction progress. The influence of main reaction parameters such as temperature, time, and catalyst load were assessed. The reaction scope was extended to the other alcohols. The activation energy of heteropolyacid-catalyzed reactions was determined.