Vitamin D is essential compound for life having role not only in the regulation of calcium metabolism but also in the regulation of cell proliferation, immune responses, cardiovascular homeostasis and nervous system. These wide range of actions occur with the enzymatic conversion of vitamin D to 1a,25-dihydroxyvitamin D by cytochrome P450 enzymes (CYPs). While CYP27B1 provides the synthesis of hormonally active form of Vitamin D, 1,25(OH)2D, CYP24A1 involves in catabolism of vitamin D. Quercetin, as one of the important member of polyphenols, is widely studied due to its abundant consumption with a diet, important role in human health as activators or inhibitors for biochemical reaction, antioxidant and anticancer activities. Recently, interaction between vitamin D receptor and quercetin has been reported at molecular level in a few studies. Quercetin may affect the expressions of vitamin D metabolizing CYP enzymes. The aim of this study was to investigate the effect of quercetin on mRNA and protein expressions of vitamin D metabolizing CYP27B1 and CYP24A1 in embryonic kidney HEK293 cell line. The effects of quercetin on CYP27B1 and CYP24A1 mRNA and protein expressions in HEK-293 cell line were determined by qPCR and western blotting techniques, respectively. Results showed that, quercetin inhibited the proliferation of HEK-293 cells in a concentration dependent manner. IC50 value of quercetin on HEK-293 cell line was found as 60.72 lM. Quercetin treatment did not significantly affect the mRNA expressions of CYP27B1 and CYP24A1. While CYP24A1 protein expression was upregulated significantly (1.38 fold), CYP27B1 protein expression was not affected significantly with quercetin treatment compared to 0.35% DMSO containing untreated cells. These results suggested that quercetin may affect vitamin D metabolism negatively in HEK293 cells due to increase in CYP24A1 protein expression.