The (bio)geochemical cycling of arsenic (As) and iron (Fe) is generally coupled in high As groundwater. However, characteristics and mechanisms of As sequestration-release behavior during formation-reduction of biogenic Fe(III) minerals (bio-FeM) are poorly understood. The Pseudogulbenkiania sp. strain 2002 induced the formation of binary bio-FeM, facilitating As immobilization compared to single Fe(III) minerals. Net As release was found during reduction of binary bio-FeM by Shewanella oneidensis strain MR-1, which was affected by secondary iron mineral formation and competitive adsorption. We suggested that bio-FeM deserve more attention due to their outstanding potential roles in controlling As behavior in aquatic systems.