Hydrogels are polymeric materials that have absorption and retention capacities of high quantity of water in their tridimensional structure. This characteristic enables the hydrogel to remove soluble and insoluble water from liquid fuels. In this context, this work aims to study the swelling kinetics of the hydrogel of acrylamide copolymerized with acrylonitrile and use it to remove water in biodiesel. The kinetic parameters and hydrophilic properties were obtained from the study of swelling of the hydrogel in free water at 25 and 40 °C. The removal of soluble water (%) in biodiesel by the hydrogel was performed in 72 h in batch experiments at 25 and 40 °C, which corresponds to the equilibrium time The hydrogel synthesized with acrylonitrile and acrylamide obtained a swelling ratio (weight of the swollen sample to that of the dry sample) of Weq = 8.46 (g water/g hydrogel) and, Weq = 7.25 (g water/g hydrogel) for 25 and 40 °C, respectively. The removal of soluble water from saturated biodiesel using poly(acrylamide-co-acrylonitrile) hydrogel was approximately 62 and 74% for 25 and 40 °C, respectively. The experiments performed showed the ability of the hydrogel synthesized to reduce water content from biodiesel.