In this study the prevalence of Escherichia coli O157:H7 was detected by immunomagnetic separation (IMS) based cultivation technique and polymerase chain reaction (PCR) in feces and/or colon tissue of cattle (n= 282) and sheep (n= 218) at slaughterhouse. The major virulence genes, intimin variants, Shiga toxin variants and antibiotic resistance genes of the isolates were examined by PCR and genomic diversity of the cattle and sheep E. coli O157:H7 isolates were assessed using pulsed field gel electrophoresis (PFGE). In the present study the prevalence of E.coli O157:H7 was found higher in sheep (6.4 %) than in cattle (3.9 %). All the E.coli O157:H7 isolates were detected as positive for at least one stx gene and positive for other virulence genes. Twelve (29.3 %) and one (2.4 %) of the cattle isolates carried stx2 and stx1 gene, respectively. However 11 (17.7 %) of the sheep E. coli O157:H7 isolates carried stx2 and five (8.1 %) of the isolates harbored stx1 gene only. At least one antibiotic resistance gene was detected from 35 isolates. E. coli O157:H7 isolates from four sheep and three cattle harbored tetB gene. From three cattle and one sheep samples strA carrying E. coli O157:H7 were isolated. Among them, isolates from 2 cattle and one sheep samples were carried both tetB and strA. Isolates were grouped into six different clusters. From a cattle and a sheep, two different E. coli O157:H7 which have different PFGE patterns, were isolated. It can be concluded that sheep pose a risk as cattle for STEC O157:H7 contamination in Turkey.