Stabilisation by nanoparticles can be considered as an efficient method for enhancing the mechanical properties of clay exposed to the freeze–thaw cycles. The laboratory tests were conducted to understand the effects of various freeze–thaw cycles on clay treated with different percentages of nano-SiO₂. In this paper, unconfined compressive strength (UCS) and shear resistance of soil, as well as the influencing mechanism of nano-SiO₂ was evaluated.The results showed that nano-SiO₂ leads to improve and prevent the resistance reduction of clay due to the freeze and thaw processes. After 9 cycles, the UCS and shear strength of clay treated with 1.0% nano-SiO₂ were 16% and 21% more than natural clay which was not subjected to the freeze–thaw cycles. Scanning electron microscopy (SEM) images represent that nano-SiO₂ produces whiskers under thermal stresses caused by freeze–thaw cycles. The whisker phenomenon leads to a significant increase in the mechanical properties of clay by creating filamentary networks.