Thermal and mechanical properties of neat linear low-density polyethylene (LLDPE) hybrid biocomposite with sugarcane bagasse and eggshell as a reinforcing filler were investigated. Hybrid biocomposites with sugarcane bagasse/eggshell was varied in the range of 6/4, 12/8, 17/13, 20/20, 13/17, 8/12, and 4/6 wt.%, were prepared and examined. The sugarcane bagasse fiber (Sb) was surface-treated using a silane coupling agent (3-(trimethoxysilyl) propyl methacrylate) and eggshell (Es) was treated using titanium (IV) isopropoxide. The results showed that high calcium oxide content was 99 % by weight in eggshell and silicon dioxide content was 50 % by weight in sugarcane bagasse. The tensile and flexural modulus and hardness of the composites with treated Sb/Es were higher than that of the untreated. These values of the LLDPE/Sb/Es composites increased with Sb/Es content. Differential scanning calorimetry (DSC) results show interesting trends in term of the influence of Sb/Es content, both with untreated and treated Sb/Es on the crystallization behavior of the composites but the melting and cold crystallization temperature of its composites did not obviously change. Thermogravimetric analysis (TGA) indicated their thermal stability of the composites, both untreated and surface-treated Sb/Es were lower than that of neat LLDPE. The sample molded from the biocomposite with surface-treated Sb/Es particles showed better dispersion of the materials inside.