The production of avocados for commercial purposes is on the rise; however, with this comes an increase in the amount of seed waste that is usually thrown away. One such byproduct of avocado fruit processing is the starch-rich avocado seeds that can be used to extract the starch. Starch is a functional component utilized in the food business to help with quality maintenance; additionally, it gains more attention for the use in biofilm preparation. The purpose of this research was to isolate starch from avocado seeds (ASS) and to prepare the superior quality starch-cellulose bio-composites. In this respect, extracted granules of ASS resulted in 31.24% yield. While characterizing, the thermal characteristics of ASS showed the paste beginning temperature was 75.3 °C, and its maximal viscosity reached 706 BU at 88.1 °C. It was found that the ASS stability at low temperatures was excellent, as indicated by the low syneresis rate of 1.51%. Further, the isolated ASS was subjected to the incorporation of cellulose fillers extracted from pseudo-stem fibers of waste Ensete ventricosum biomass to develop a high-performing bio-composite film (BCF). The percentages of crystallinity were as found to be 29.8% for raw ASS, 5.6% for the biofilm using starch only, and 12.3% for starch with 15% cellulose. Further, the bio-composite having 15% cellulose showed appreciable tensile strength, Young’s modulus, and elongation at break, values which were determined to be 18.0 MPa, 1782.4 MPa, and 1.5%, respectively. It was ensured that the films have been benefited from cellulose inclusion because the filler dispersion was maximized, allowing for better mechanical properties. Such a study on improving starch-based film properties hinted at a promising approach for developing upgraded bio-composites to apply to futuristic food packaging applications by exploiting fruit waste.