High temperature is one of the main environmental factors causing economic losses to the poultry industry, as it reduces growth and production performance of chickens. The heat shock proteins (HSPs) play a key role in cellular defense mechanisms during exposure in a hot environment. The aim of this study was to evaluate the expression level of the candidate genes in the liver of Khorasan native chickens under acute heat stress. Sixteen 42 days old chickens were divided into two groups; the control (25 ˚C and 50% humidity) and heat-treated (42 ˚C and 50% humidity), and then the liver was sampled. The level of gene expression of HSPB1, HSPB9, SERPINH1, HSPA2 and HSP110 were evaluated using the reverse transcription- quantitative polymerase chain reaction (RT-qPCR) method. The results of the analysis of variance revealed that the expression of HSPA2 and HSP110 was significantly increased. In the biological processes of gene ontology, three processes had FDR < 0.01. HSPA2 and HSPB1 involved in the processes that stimulated cells against increasing temperature. The results indicated that Khorasan native chickens have suitable resistance to acute heat stress. Furthermore, HSPA2 has the ability to express under high ambient temperature in order to protect the structure of cellular proteins. Manuscript profile