The red flour beetle, Tribolium castaneum (Herbst) (Col.: Tenebrionidae), is an important insect pest of stored products, including broken grain, milled grain products, beans, nuts, crackers, spices, pasta, dried fruits, and dried flowers. To overcome adverse effects of low temperature, several physiological mechanisms have been developed in insects of cold and temperate zones. In the present study, we hypothesize that variation in cold tolerance of T. castaneum adults under different thermal regimes, i.e. control, cold-acclimated (CA), fluctuating-acclimated (FA) and rapid cold-hardened (RCH) arises from change in the cryoprotectant contents in the cold. Data showed that under CA thermal regime supercooling point of the adults reached to the lowest level (-18.4 ºC), which significantly lower than SCP of control insect (-10.7 ºC). Also, significant differences were observed between SCP of control with FA (-16.1 ºC) and RCH (-14.2 ºC) thermal regimes. The results of present study showed a profound effect of CA on the LT80 value of the adults. LT80 values of the adults at control, RCH, FT and CA regimes were calculated as -11.1, -14.9, -16.8 and -19.8 ºC, respectively. In CA adults, the temperature required for 80% mortality decreased about 8 ºC compared with control insects. In addition, the temperature necessary for the beginning of mortality in CA regime was 9 ºC lower than that of control. Trehalose, sorbitol, myo-inositol and glucose were found to be the main low molecular weight of carbohydrates in all the thermal regimes. The highest and lowest contents of trehalose and sorbitol were observed in CA (14.8 and 4.1 mg/dry weight) and control (6.6 and 2.5 mg/dry weight), respectively. similarly, the highest and lowest myo-inositol contents were observed in CA (11.8 mg/dry weight) and control (5.4 mg/dry weight), respectively. No significant difference was observed in glucose content between control and different thermal regimes. Our results showed a significant enhancement of adults’ cold tolerance under CA regime that is related to the elevated level of low molecular weight carbohydrates, mainly trehalose and myo-inositol.