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Freshwater re-flooding is a relatively novel approach to remediate drained acid sulfate soil (ASS) wetlands. This study documents the geochemical consequences of restoring freshwater re-flooding for contemporary reduced inorganic sulfur (RIS) and iron species in two coastal floodplain ASS wetlands. Re-flooding has established predominantly reducing/suboxic conditions and encouraged organic carbon accumulation in surface sediments (~ 20–30%). The pH of former sulfuric horizons has increased by ~ 2–3 units, partly in response to alkalinity generation from anaerobic metabolism of organic carbon coupled with Fe(III) and SO₄^2 − reduction. Despite considerable sulfidisation, reactive Fe (Fe_R; sum of 1 M HCl and citrate–dithionite extracts) and non-sulfidic Fe(II) remain abundant in both wetlands. High concentrations of Fe^2 + (up to ~ 5 mM) in wetland porewaters represent a considerable pool of labile net …