•Presenting the relationship between fracture toughness and the number of freeze–thaw cycles.•Presenting the relationship between fracture toughness and freezing temperature.•Analysis of X-ray CT to investigate the damage caused by the freeze–thaw cycles. The freeze–thaw process is one of the natural phenomena significantly affecting the characteristics of rocks and their properties. This study aimed at investigating the effects of freeze–thaw cycles and freezing temperature on mode I and mode II fracture toughness of Lushan sandstone. To this end, specimens were exposed to 0, 5, 10, 20 and 30 freeze–thaw cycles, and mode I and mode II fracture toughness were evaluated in different cycles. The effect of freezing temperature in a freeze–thaw cycle on mode I and mode II fracture toughness was also investigated. X-ray computerized tomography (CT) was used to determine specimen damages caused by freeze–thaw cycles. According to the results, mode I and mode II fracture toughness nonlinearly decreased with increasing the number of freeze–thaw cycles. The CT photographs showed an increase in the damage factor caused by freeze–thaw cycles. The mode I and mode II fracture toughness of Lushan sandstone nonlinearly decreased with increasing the freezing temperature in the freeze–thaw process.