Starch-based polymers such as polylactic acid (PLA) are increasingly used in biomedical devices, medical tools and packaging due to their biodegradability, biocompatibility and good processability. In this study, biofilms were prepared using PLA, tapioca starch and glycerol. A PLA-to-starch ratio of 70:30 (w/w) was maintained with glycerol added at concentrations of 4, 8, 12, 16 and 20 ml. Mechanical testing showed that the 4 ml glycerol film had the highest tensile strength, while higher glycerol levels improved flexibility. Soil burial tests revealed that the 12 ml glycerol sample degraded completely within 28 days. Water solubility and swelling increased with glycerol content due to its hydrophilic nature. FTIR analysis confirmed hydrogen bonding between PLA, Tapioca starch and glycerol, with peak shifts in hydroxyl and carbonyl regions. SEM images indicated smoother and more uniform surfaces at higher glycerol concentrations, suggesting improved compatibility. TGA results showed a slight reduction in thermal stability with increased glycerol, attributed to greater chain mobility. These findings demonstrate that glycerol content significantly influences the mechanical, thermal and biodegradation properties of PLA–starch biofilms.