Selenoprotein P (Sepp1) is taken up by receptor‐mediated endocytosis for its selenium. The other extracellular selenoprotein, glutathione peroxidase‐3 (Gpx3), has not been shown to transport selenium. Mice with genetic alterations of Sepp1, the Sepp1 receptors apolipoprotein E receptor‐2 (apoER2) and megalin, and Gpx3 were used to investigate maternalfetal selenium transfer. Immunocytochemistry (ICC) showed receptor‐independent uptake of Sepp1 and Gpx3 in the same vesicles of d‐13 visceral yolk sac cells, suggesting uptake by pinocytosis. ICC also showed apoER2‐mediated uptake of maternal Sepp1 in the d‐18 placenta. Thus, two selenoprotein‐dependent maternalfetal selenium transfer mechanisms were identified. Selenium was quantified in d‐18 fetuses with the mechanisms disrupted. Maternal Sepp1 deletion, which lowers maternal whole‐body selenium, decreased fetal selenium under selenium‐adequate conditions but deletion of fetal apoER2 did not. Fetal apoER2 deletion did decrease fetal selenium, by 51%, under selenium‐deficient conditions, verifying function of the placental Sepp1‐apoER2 mechanism. Maternal Gpx3 deletion decreased fetal selenium, by 13%, but only under selenium‐deficient conditions. These findings indicate that the selenoprotein uptake mechanisms ensure selenium transfer to the fetus under selenium‐deficient conditions. The failure of their disruptions (apoER2 deletion, Gpx3 deletion) to affect fetal selenium under selenium‐adequate conditions indicates the existence of an additional maternal‐fetal selenium transfer mechanism.—Burk, R. F., Olson, G. E., Hill, K. E., Winfrey, V. P., Motley, A. K., and Kurokawa, S., Maternal‐fetal transfer of selenium in the mouse. FASEB J. 27, 3249–3256 (2013). www.fasebj.org