Nowadays, the demand for starch-based adhesive has increased from time to time as well as from year to year, which can replace petroleum-derived adhesives and have a great impact on the environment issues. Adhesives can be made from any source of starch. Currently, the applications of starch-based adhesive are somehow limited due to the lack of gap-filling materials. Starch-based adhesive was improved using clay particles as a reinforcing agent. The aim of this study is to develop and characterize sustainable bio-based adhesive from avocado seed starch using clay particle as a filler. In this research, the main factors that are taken into account are glycerol and clay (kaolin). The adhesive was developed based on the experimental design with clay to starch ratios of 0.5:1, 0.2:1, 0.3:1 w/w and glycerol to starch ratios of 2.5:1, 5:1, 7.5:1 w/v, respectively. The effects of the two parameters on the adhesive properties were observed. The developed adhesive was characterized in terms of physicochemical and thermomechanical properties. In the experimental analysis, the optimum hot melt viscosity (3.11 ± 0.31 cp), moisture content (12.41 ± 0.09%), tensile strength (3.45 ± 0.22 MPa), and shear strength (3.135 ± 0.170 MPa) were determined. These all-optimum values were obtained at the ratios of 1:5 filler to plasticizer ratios and keep in mind that the amount of starch was kept constant (5 g). Based on the present experimental result, the optimum shear strength of the adhesive in dry state was found to be 3.135 ± 0.170, while in the wet state was 1.105 ± 0.02 MPa. The FTIR analysis indicated that there was good interaction among the constraints of the adhesive such as filler material, the starch, and plasticizer.