The use of elevated temperatures or heat treatments for managing insect pests in food-processing facilities is becoming a popular alternative to methyl bromide fumigation. We found that young larvae (first instars) of red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), were relatively more tolerant to elevated temperatures than eggs, old larvae, pupae, and adults. Our objective was to determine whether heat shock proteins (HSPs) confer thermotolerance in T. castaneum life stages. Western blot analyses by using HSP 70 antibody showed constitutive expression of HSP 70 in all stages of T. castaneum. However, the expression of HSP 70 in young larvae increased by ≈33%, after the larvae were exposed to 40°C for 1 h. The expression of HSP 70 in other stages did not vary significantly, but for eggs the expression of HSP 70 showed significant reduction at 40°C. Young larvae possessed two distinct HSPs with molecular masses of 70 and 24 kDa, both recognized by a monoclonal anti-bovine brain HSP 70 antibody. Our study suggests that increased thermotolerance in young larvae could be due to increased expression of HSP 70 at higher temperatures. Time- and temperature-dependent expression of HSP 70 showed that the increased thermotolerance in young larvae might last as long as 8 h at 40°C or 30 min at 46°C.