In today’s world, no one can stand without plastic. These ingredients are enormously dependent on several industries including aerospace, food packaging, automotive, plastic shopping bags, and many more. Landfills are full of plastic waste and the accumulation of plastic waste in the environment caused many problems. Plastic shopping bags are made from polyethylene, which causes environmental problems as they are resistant to degradation so they stay in the environment for a long time. In the meantime, there are various options to reduce the environmental problems by increasing the use of biopolymers. In the present study, a mixture of organic compounds of polyethylene and bio-based fillers (sago starch, SS) was prepared. SS was modified with starch cross-linker. Samples with different levels of unmodified starch and the same amount of modified SS was mixed with polyethylene using different additives were fabricated by melt blending method tracked by injection molded to form composites. The loss of tensile strength of the modified composite was less but more elongation at break than unmodified composite, which indicates a good interfacial bond between polyethylene and SS. The biodegradation behavior of these composites was observed in terms of weight loss, morphology, and tensile features during water environment and soil burial.