Molybdenum is an essential element for most biological systems. Biosynthesis of Mo-enzymes that support global biogeochemical cycles of N, C, and S depends upon bioavailable molybdate (MoO₄²⁻). Interactions with Fe(III) (oxyhydr)oxides can limit Mo bioavailability in aerobic environments, while redox-driven mineral transformations can enhance Mo sequestration. Here, we examine Mo repartitioning during Fe(II) and S(-II) driven ferrihydrite transformation under anaerobic conditions. We reacted Mo(VI) co-precipitated 2-line ferrihydrite with Fe(II)_(aq) or S(-II)_(aq) and monitored geochemical and mineralogical changes over time. Inductively coupled plasma–mass spectrometry (ICP–MS) and synchrotron powder X-ray diffraction (XRD) results revealed rapid Fe(II)_(aq) and S(-II)_(aq) uptake and limited Mo release during extensive ferrihydrite transformation to goethite [α-FeOOH] and lepidocrocite [γ-FeOOH] in the Fe(II) and S(-II) experiments. Transmission electron microscopy–selected area electron diffraction (TEM-SAED), coupled with Mo L_III-edge and K-edge X-ray absorption near edge structure (XANES) spectroscopy, revealed partial Mo(VI) reduction and precipitation of kamiokite [Fe₂Mo^IV₃O₈] and sidwillite [Mo^VIO₃‧2H₂O] in both experiments. Extended X-ray absorption fine structure (EXAFS) spectroscopy at the Mo K-edge revealed MoO, MoFe and MoMo bonding consistent with kamiokite precipitation in both Fe(II) and S(-II) experiments, and the absence of MoS bonding in the S(-II) experiments. Similar Mo(VI) repartitioning pathways during Fe(II) and S(-II) driven ferrihydrite transformation suggests that: (i) Fe(II) served as the electron donor for ferrihydrite transformation in both experiments, with Fe(II)_(aq) likely produced in situ via ferrihydrite sulfidation in the S(-II) experiments; and (ii) co-precipitation inhibited Mo release and limited subsequent interactions S(-II)_(aq) during ferrihydrite transformation. Overall, our findings indicate that initial association with FeOx phases can strongly influence Mo sequestration pathways in anaerobic environments.