The majority of iron for essential mammalian biological activities such as erythropoiesis is thought to be reutilized from cellular hemoproteins. Here, we generated mice lacking functional heme oxygenase 1 (Hmox1; EC 1.14.99.3), which catabolizes heme to biliverdin, carbon monoxide, and free iron, to assess its participation in iron homeostasis. Hmox1-deficient adult mice developed an anemia associated with abnormally low serum iron levels, yet accumulated hepatic and renal iron that contributed to macromolecular oxidative damage, tissue injury, and chronic inflammation. Our results indicate that Hmox1 has an important recycling role by facilitating the release of iron from hepatic and renal cells, and describe a mouse model of human iron metabolic disorders.