The investigation on thermal properties of nanoparticles dispersed in the mixture of water and green Bio-glycol are limited in the literature and only available for single nanofluids. The purpose of this study is to investigate the stability and thermo-physical properties of green Bio-glycol based TiO2-SiO₂ nanofluids. In the present study, the hybrid nanofluids were prepared at various volume concentrations of 0.5 to 3.0% by dispersing TiO₂ and SiO₂ nanoparticles (20:80) in water and Bio-glycol (40:60) mixture base fluids. The stability of green Bio-glycol based TiO₂-SiO₂ nanofluids showed physically to be in good range of stability for suspension nanoparticles with zeta potential of - 53.46 mV. The thermal conductivity of the green Bio-glycol based TiO₂-SiO₂ nanofluids was enhanced up to 12.52% higher than the mixture of W/BG at 3.0% volume concentration and temperature of
70◦C. Meanwhile, there is insignificant dynamic viscosity increment of the green Bio-glycol based TiO₂-SiO₂ nanofluids with temperature. As a conclusion, a stable TiO₂-SiO₂ hybrid in green Bio-glycol/water mixture nanofluids was formulated in the present study with significant enhancement in thermal properties and recommended for heat transfer application. Further heat transfer investigation is required to confirm the feasibility of the green coolant.