<p>Cooling shock significantly deteriorates rocks' mechanical and physical characteristics in high-temperature environments. Hence, it is crucial to comprehend how high-temperature rock responds to liquid nitrogen (LN₂) cooling in the lab to support thermal application systems. This study aimed to determine how cooling preheated Egyptian granodiorite up to 600 °C with liquid nitrogen affects its microstructure, physical characteristics, and mechanical properties. Macroscopic properties like density, P-wave velocity, porosity, permeability, and uniaxial compressive strength were investigated as a function of microscopical development. The experimental results indicated that while permeability and porosity moderately enhance up to 300 °C, density and P-wave velocity show a decreasing trend with temperature. On the other hand, uniaxial compressive strength intensified before falling linearly as the temperature went up. These parameters altered more noticeably as the heating temperature rose. Hence, after LN₂-cooling beyond 300 °C, the heated granodiorite’s permeability and porosity substantially increased while density, P-wave velocity, and strength drastically decreased. According to this investigation, the characteristics of preheated granodiorite and the LN₂-cooling strategy have a transition point of 300 °C, excluding a P-wave velocity of 200 °C. Consequently, granodiorite’s mechanical, physical, and microstructure qualities severely deteriorated after these threshold temperatures. Liquid nitrogen cooling has also made it easier for microcracks to spread quickly through high-temperature granodiorite, decreasing its mechanical strength. Thus, when Egyptian granodiorite is thermally treated with LN₂, it becomes much more porous and permeable, making it a good choice for improved geothermal systems.</p>