We examined the effect of dietary iron concentration on the incidence of hepatic hemosiderosis in common marmosets (Callithrix jacchus) and assessed the impact of hemosiderosis on animal health. Thirteen young adult common marmosets were fed nutritionally balanced natural-ingredient diets formulated to contain either 100 or 500 ppm of iron. Six were fed the low-iron and seven received the high-iron diet. Baseline blood values and liver iron content were determined for each animal. Animals were weighted monthly, blood work (hematologic analysis, serum iron concentration, total iron-binding capacity, percent of transferrin saturation) was performed semi-annually, and liver biopsies for iron analysis were obtained after marmosets had consumed the test diets for 13 months or at necropsy. Midway in study, the high-iron diet was reformulated to contain 350 ppm of iron because of the death of a male which had consumed that diet for 7 months. Four of seven marmosets fed the high-iron diet died during the first year of the study, compared with one death in the low-iron cohort. The mean increase in liver iron content of the marmosets fed the high-iron diet was 6,371 micrograms/g, dry weight analysis. In contrast the low-iron cohort had a mean decrease of 621.5 micrograms/g. These results indicate that liver iron content can be affected by dietary iron intake. The increased mortality in the marmosets fed the high-iron diet also suggests that hepatic hemosiderosis can be detrimental to marmoset health.