Several alternatives have been considered to minimize the environmental impact caused by conventional polymers. This study aims to evaluate the chemical, mechanical and morphological properties of flexible thermoplastic films of cassava and corn starch, using glycerol and lignin as plasticizers and reinforcement. The films were produced through casting. It was observed that the presence of lignin effectively increased the maximum stress and the elastic modulus by about of 840% and 4200%, respectively, when comparing to the film containing only glycerol. In addition, lignin improved thermal properties, modified some structural properties and made the surface of the material rougher.