<p>In this study, two-dimensional hexagonal boron nitride nanosheets are prepared using green synthesis approach. Here, <i>Solanum Lycopersicum</i> leaf extract is used as stabilizing agent. The structure and morphology of green-synthesized two-dimensional hexagonal boron nitride nanosheets (GS 2D h-BNNSs) are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), field-emission-scanning electron microscope (FE-SEM) and high-resolution transmission electron microscope (HR-TEM). Thickness and nature of the surface are determined by atomic force microscope (AFM). The as-prepared GS 2D h-BNNSs are then dispersed in pure EG and different combination of EG/water mixture to obtain 0.2, 0.4 and 0.6&#xa0;g L⁻¹ of nanofluids and are investigated for its stability, thermophysical properties and contact angle. The stability of 0.6&#xa0;g L⁻¹ of GS 2D h-BNNSs nanofluids with 50:50% of EG/water has a zeta potential value of + 61.7&#xa0;mV, indicating excellent stability. In comparison with pure EG, a maximum enhancement in thermal conductivity of 82.29% is obtained with 0.6&#xa0;g L⁻¹ concentration of 50:50% EG/water nanofluids at 60 °C. Viscosity of nanofluids increases with concentrations for all the combinations of base fluids. However, viscosity decreases with temperature and discloses a lowest viscosity of about 1.85 cP for 50:50% EG/water combination with 0.2&#xa0;g L⁻¹ at 60 °C. Wettability of copper, aluminium and mild steel substrates is investigated and the copper substrate with a mixture of 90:10% EG/water at 0.6&#xa0;g L⁻¹ of GS 2D h-BNNSs nanofluids discloses excellent contact angle of 8°.</p>