Mg deficiency accelerates Fe accumulation in the liver, which may induce various metabolic disturbances. In the present study, we examined the gene expression of Hepcidin, a peptide hormone produced in the liver to regulate intestinal Fe absorption negatively, in Mg-deficient rats. Although liver Fe concentration was significantly higher in rats fed an Mg-deficient diet for 4 weeks than in rats fed a control diet, Hepcidin expression in the liver was comparable between the dietary groups. Previous studies revealed that Fe overload up-regulated Hepcidin expression through transcriptional activation by Fe-induced bone morphogenetic protein (Bmp) 6, a growth/differentiation factor belonging to the transforming growth factor-β family, in the liver. Mg deficiency up-regulated the expression of Bmp6 but did not affect the expression of inhibition of DNA binding 1, a sensitive Bmp-responsive gene. In addition, the expression of Bmp receptors such as activin receptor-like kinase 2 (Alk2), activin receptor type IIA (Actr2a), activin receptor type IIB (Actr2b) and Bmp type II receptor (Bmpr2) was lower in the liver of Mg-deficient rats than in that of control rats. The present study indicates that accumulation of hepatic Fe by Mg deficiency is a stimulant inducing Bmp6 expression but not Hepcidin expression by blunting Bmp signalling possibly resulting from down-regulation of the receptor expression. Unresponsive Hepcidin expression may have a role in Mg deficiency-induced changes related to increased liver Fe.