The transcription factor KLF6 gene has been identified as a tumor suppressor because of its inactivation in several types of cancers by different mechanisms. However, there are no data in the literature investigating the KLF6 mutation rate and expression levels in breast cancer. Therefore, the present study was conducted in order to investigate whether genetic alterations of KLF6 in association with the KLF6 mRNA expression levels may play a role in breast carcinogenesis. For this purpose, we analyzed alterations of the KLF6 gene by direct sequencing and the mRNA levels by reverse transcription-PCR (RT-PCR). In addition to four different non-coding alterations, one missense and two silent alterations were identified in the coding sequence. Reduced KLF6 expression was observed in 41 (83.67 %) of the 49 breast cancer tumors. These findings suggest that the mutation profile of the KLF6 gene in breast tumors is similar to other cancer types. However, these mutations do not exert any effect on the gene expression rate. Downregulation of KLF6 during the progression of breast cancer is independent of the mutations and occurs by a different mechanism.