Iron deficiency is the most common type of nutritional deficiency in the world, and calcium intake is low in many populations. Developing a supplement that contains both micronutrients would be an excellent method to prevent iron deficiency and increase calcium intake. Human and cellular studies have shown that calcium inhibits iron absorption. Currently, the mechanisms underlying this inhibitory effect have not been elucidated. Because calcium is involved in cell signaling pathways, it may affect the regulation of the expression or localization of proteins involved in iron uptake and efflux in enterocytes. The aim of this review was to describe the processes involved in the absorption of dietary iron and the regulation of the expression and activity of proteins involved in this absorption. Additionally, the potential mechanisms by which calcium affects the expression and localization of these proteins are also discussed.