The reductive release of iron from ferritin by UV light or ionizing radiation has been investigated in separate experiments. When ferritin is exposed to light, the mineral core is the main photoreceptor for the Fe(III) reduction. In radiolytic studies, we determined that, in the absence of oxygen, the hydrated electron (eaq−) is the reducing agent triggering redox reactions associated with iron mobilization from ferritin. In an aerobic system, the superoxide radical anion (O2•−) is also involved in the iron release process. We found that, in photochemical and radiolytical studies, Fe(II) mobilization from ferritin required an iron chelator. Without a chelator, ferritin is an electron-storage molecule for a long period, on the order of at least several hours. The reductant or chelator entry into the ferritin core is not necessary for iron release. The ferrozine is a convenient chelating agent to monitor Fe(II) mobilization, due to a high extinction coefficient of $ {\text{Fe}}\,\left( {\text{ferrozine}} \right)_{3}^{4 - } $ and a high rate constant of complexation process (2.65 × 104 dm3 mol−1 s−1).