Background: The body's requirement of iron is different at different developmental stages. However, the molecular mechanisms of iron metabolism with age are poorly understood. In the present study, we investigated the expression of iron transport proteins in the duodenum of sprague–dawley (SD) rats among five periods of age. Methods: Male SD rats at postnatal week (PNW) 1, 3, 12, 44, and 88 were used. Serum iron status and tissue non-heme iron concentrations in spleen, liver, bone marrow, heart, kidney, duodenal epithelium, and gastrocnemius were examined. The expression of duodenal cytochrome B561 (DcytB), divalent metal transporter 1 (DMT1), ferroportin1 (FPN1), hephaestin (Hp), and hepcidin were measured by real-time PCR or Western blot. Results: The levels of serum iron (SI) and transferrin saturation (TS) were higher in rats of PNW1 and 3 than in rats of PNW12, 44, and 88. Non-heme iron contents were decreased from PNW1 to PNW3, and then increased with age. DcytB, DMT1, and FPN1 showed the highest level in PNW3 and then decreased in PNW12, 44 and 88. There was no significant change of Hp expression in duodenum. The hepatic hepcidin mRNA level was lowest in rats of PNW3, and then increased with age. Conclusions: Our findings showed that age had a significant effect on body iron status. The increased duodenal DcytB, DMT1, and FPN1 expression can enhance intestinal iron absorption to meet the high iron requirements in infants. Hepcidin or enterocyte iron levels may be involved in the regulation of age-dependent FPN1 and DMT1 expression in duodenum.