The shear behavior of clays is critically important for the stability and safety of nuclear waste repositories and clay gouges. These contexts expose clayey geomaterials to high pressures and temperatures. Under such varying thermodynamic conditions, the shear behavior of these materials becomes complex, necessitating thorough investigations. This study aims to elucidate the effect of temperature on the shear behavior of non-swelling clayey materials—kaolinite and illite—through molecular dynamics simulations. The research replicates a geotechnical shear setup at the molecular scale, varying the environmental temperature including sub-freezing temperatures below 300 K and elevated temperatures in the range of 300-500 K and hydrostatic pressure. The results reveal stick-slip behavior, enabling the calculation of nanoscale cohesion, friction angle, and shear modulus across different temperatures. Thermal effects are notably significant for illite and kaolinite, both exhibiting a marked decrease in shear properties with increasing temperature. Kaolinite demonstrates a high shear modulus of up to 40 GPa, indicating substantial shear strength compared to illite.