Banded iron formations (BIFs) are chemical sedimentary deposits that record interactions among seawater, hydrothermal fluids, volcanic activity, and redox conditions in the early Earth. The Rezvan iron deposit, located in the Zagros Fold–Thrust Belt of southern Iran, is hosted by volcano–sedimentary successions comprising carbonate, volcaniclastic, and intermediate volcanic rocks. This study presents the first integrated geological, petrographic, mineralogical, and geochemical investigation of the deposit to constrain its genetic evolution and depositional setting. Mineralization occurs as stratiform to lens-shaped bodies and records a multistage evolution, including early hematite ± magnetite, subsequent pyrite ± chalcopyrite mineralization, and late supergene goethite–limonite alteration. Low concentrations of Al, Ti, Zr, and Sc indicate limited terrigenous input and support a predominantly chemical marine origin. Chondrite-normalized REE patterns show low total REE concentrations, slight LREE enrichment, weak negative Ce anomalies, and locally positive Eu anomalies, indicating seawater deposition influenced by hydrothermal fluids under predominantly oxidizing conditions. Integrated evidence indicates that the deposit initially formed through chemical precipitation of iron and silica in a volcanically active shallow-marine basin, followed by hydrothermal sulfide overprinting and supergene alteration. The Rezvan deposit is therefore interpreted as an Algoma-type BIF formed in a shallow, hydrothermally influenced volcano–sedimentary marine environment during the Proterozoic era.