Although the main storage organ for iron is liver, the kidneys maintain the state of general homeostasis, but also the homeostasis of transition metals by filtration and reabsorption. In rat kidneys, as well as in the liver, the iron content shows sex and age differences in favor of females vs. males, and increases in both with age. Iron is stored in the form of a ferritin complex, the nanocage built of a total of 24 subunits. Light (FtL) and heavy (FtH) subunits form a hollow sphere that can store up to 4500 iron atoms in bioavailable form. Sex and age differences in iron accumulation in the liver and kidneys were determined by the earliest research and subsequently related to the level of ferritin. Known sex differences of the ferritin complex in the kidneys, which reflect iron content, have not been investigated by monitoring ferritin subunits individually so far, nor has the effect of sex hormones and aging been established. This work studied the effect of sex, gonadectomy, and aging on the distribution and presence of FtL and FtH in the kidneys of three-month and two-year-old experimental animals using immunochemical methods. The results indicate that pronounced sex differences in favor of females for both FtL and FtH that exist in mature animals following iron accumulation, and are determined to a lesser extent by the positive effect of estrogen, and by the negative effect of testosterone. With aging, the presence of FtL and FtH in both sexes strongly increases, not following the accumulation of iron in the kidneys of males and females. Even protected in ferritin, this iron could be responsible for a higher sensitivity of the kidneys, but also the whole organism to reactive oxygen species in old age and after any kind of insult in old age. The model of sex and age differences in iron and ferritin accumulation is an excellent basis for studying the physiology of transition metals and proteins that accompany them, but also possible interventions for healthier aging.