Microbial, anoxygenic phototrophic ferrous iron (Fe(II)) oxidation (pFeOx) plays an important role in biological iron cycling. The uptake and oxidation of dissolved Fe(II) species (Fe2+aq) as an electron donor for pFeOx bacteria is well understood. In contrast, the oxidation of solid Fe(II)-bearing minerals by pFeOx is less well studied, with possible mechanisms including dissolution of the minerals followed by uptake and intracellular oxidation of Fe2+aq or extracellular electron transfer from solid Fe(II) minerals to the bacterial cells. We investigated the oxidation of the Fe(II)-bearing carbonate mineral siderite (FeCO3) by an anoxygenic phototrophic Fe(II) oxidiser Rhodopseudomonas palustris TIE-1. We aimed to explain if oxidation was controlled by chemical dissolution kinetics or whether direct electron transfer was involved. Controlled dissolution experiments using increasing dissolved bicarbonate concentrations (0–300 mM HCO3–), supported by geochemical modelling, demonstrated that R. palustris TIE-1 can oxidise up to 5-fold more Fe(II) when cells are in direct contact with siderite than would be expected if oxidation occurred through dissolution alone. These results suggest that anoxygenic phototrophic Fe(II)-oxidising bacteria have the capability to enhance carbonate dissolution or even access solid-phase Fe(II) in siderite as a source of electrons, especially when siderite dissolution is limited or suppressed by geochemical constraints.