Some wild species of mammals and birds are prone to excessive iron accumulation, especially when maintained in human care. Hemosiderosis is the process of intracellular accumulation of iron without evidence of toxicity, whereas hemochromatosis is characterized by severe iron accumulation with accompanying organ damage. Iron storage disease (ISD) occurs when organ damage is severe and causing clinical signs. This retrospective study investigated the occurrence of hemosiderosis and ISD across a variety of avian taxa, including captive and free-ranging birds. Archived paraffin-embedded hepatic samples from 103 birds from Belo Horizonte Zoo that died naturally in the period of 2008 to 2018 were re-evaluated with histologic and morphometric techniques, focusing on the identification and scoring of iron deposits in hepatocytes and the quantification of total affected hepatic area. The birds represented 13 orders, 22 families, and 52 genera, and 66 (64.0%) had some degree of iron accumulation in their liver. Importantly, no statistical difference was observed in the occurrence of iron accumulation between families, orders, or origin (free-ranging or captive). Direct and positive correlation was observed between the total area affected by the iron deposits and the histologic score. In this study, there were two cases with severe iron accumulation and clinical signs compatible with ISD: a barefaced curassow (Crax fasciolata) and a channel-billed toucan (Ramphastos vitellinus). This study indicates that iron accumulation may occur in a wide range of avian species, with frequencies and intensities that are similar between free-ranging birds and those in human care. It describes for the first time the occurrence of ISD in a Galliform species.