Waste cassava starch was soaked in water for 24 h and the solution was heated at 70 °C that was then plasticized by using different plasticizer such as glycerine, sorbitol, and polyethylene glycol separately (0%–40% with respect to starch). This was blended with polyvinyl alcohol (PVA) matrix in aqueous solution. Plasticizer content (Plc) was varied from 10% to 40% with respect to starch. The solutions were cast into films in a plastic dish and dried at 55 °C for 24 h. These were subsequently given short-time heat treatment (150 °C for 2 min). The films were characterized by XRD, FTIR and tested for mechanical properties and seal strength. The two prominent XRD peaks at 19.6° and 23° merge in one broad peak for high Plc percentage. The crystallinity (Ci) decreased with the increase of Plc percentage in the order PEG < sorbitol< glycerine. Increase in the content of PVA led to a shift of onset degradation temperature to higher value while an increase of Plc percentage it lowered slightly. The FTIR bands in the region of 1130–1020 cm−1 indicated crystal modification of starch after heating. The tensile strength decreased with the increase in Plc percentage but increased after heat treatment (even for Plc percentage of 30%–40%). The elongation increased considerably with Plc percentage but dropped after heat treatment. The seal strength increased with the increase of plasticizer content. There was optimum PVA concentration (66.6%) at which best seal strength was achieved. These results correlated well with the structural changes noted with respect to composition and annealing. The above study helps to develop ecofriendly packaging films and improvements in the seal strength of such films in presence of modified starch. © 2022 by Apple Academic Press, Inc.