¹Central Research Laboratory (NABILTEM), Tekirdağ Namık Kemal University, TR-59000 Tekirdağ - TÜRKİYE DOI : 10.9775/kvfd.2022.27152 Heat stress causes a decrease in the productivity of livestock by negatively aff ecting some important economic features such as fertility, growth and milk production. Th e heat shock transcription factor 1 (HSF1) gene plays a key role in the regulation of the stress response. Th erefore, the present study aimed to predict the most deleterious non-synonymous single nucleotide polymorphisms (nsSNP) on the cattle HSF1 gene via in silico analyses. Out of 170 nsSNPs in the HSF1 gene, 14 SNPs were predicted as deleterious by all the nine servers (PredictSNP, Mapp, PhDSNP, PolyPhen-1, PolyPhen-2, Sift , Snap, nsSNPAnalyzer, and Panther). Consurf analysis determined that the vast majority of SNPs predicted to be deleterious were evolutionary conserved. Protein structural analyses were performed I-Mutant, Mupro, Hope Project server, RaptorX and Swiss Model server. Th e 12 amino acid substitutions (V15G, F18L, L19R, K21M, I35T, V46E, V56G, F61L, A67D, Y76D, V81G, L112P) in the DNA binding region of the cattle HSF1 protein were predicted to be highly deleterious. Th e P112 variant was predicted to disrupt an α-helix structure. It was determined that the two amino acid changes (K21M, Y76D) on the surface of the protein were diff erent in terms of hydrophobicity, charge, and size. Th ese variants (M21, D76) might hamper the protein"s interaction with the heat shock elements. Keywords : HSF1, Heat stress, Cattle, nsSNP, HSP