Titanium dioxide/polystyrene (TiO2/PS) core-shell nanoparticles (CSNPs) reinforced linear low density polyethylene/poly (lactic acid) (LLDPE/PLA) blends were developed by means of compounding and injection moulding. TiO2/PS CSNPs were prepared by ultrasound-assisted method while PLA was prepared by polycondensation of l-lactic acid, and were added to commercial grade LLDPE. The morphological analysis, carried out by electron microscopy, revealed significant phase separation in LLDPE/PLA blends but showed improved compatibility in LLDPE/PLA (TiO2/PS) nanocomposites. The thermal behaviour of the nanocomposites, as observed from thermogravimetric analysis (TGA), was also improved as compared to its blend counterparts. The incorporation of TiO2/PS CSNPs also resulted in better mechanical properties. With the addition of 1 phr TiO2/PS CSNPs, the tensile strength and elongation of LLDPE/PLA/(TiO2/PS) nanocomposites increased significantly. The results demonstrate the effect of TiO2/PS CSNPs in providing better interfacial adhesion between LLDPE and PLA which led to significant improvement in the mechanical strength of the nanocomposites by allowing effective load transfer in the nanocomposites system. [GRAPHICS] .