Runx2 promotes metastatic ability of cancer cells by directly activating some of the mediators regarding malignancy. Galectin-3 (Gal-3) extensively expressed in normal and transformed cells and it is responsible for many cellular processes. In this study, we aimed to investigate whether there is any relationship between runx2 transcription factor and regulation of galectin-3 expression in different human thyroid carcinoma cell lines. To show effects of runx2 transcription factor on gal-3 expression, we developed runx2 knockdown model in the thyroid carcinoma cell lines; anaplastic 8505C and 8305C and, papillary TPC-1 and follicular FTC-133 by using siRNA transfection. We analyzed the protein expressions and mRNA levels of gal-3 and MMP2/9 in the runx2-silenced cell lines using Western blotting, qPCR, and fluorescent microscopy. Our results showed that mRNA expression levels of gal-3 and MMP2/9 were downregulated in runx2-silenced cell lines. In this investigation, we revealed that regulation of gal-3 expression was strongly correlated with runx2 transcription factor in human thyroid carcinoma. Considering the contribution of human gal-3 in collaboration with MMP2/9 to the malignant characters of many cancers, regulation of their expressions through runx2 seems like one of the key regulatory mechanism for malignant potential of human thyroid carcinoma. Accordingly, runx2 transcription factor inhibitors can be a potential target in order to prevent gal-3 mediated malignancy of human thyroid carcinoma. J. Cell. Biochem. 118: 3911-3919, 2017. (c) 2017 Wiley Periodicals, Inc.