This study investigated the sequestration of dissolved selenate (SeO42-) via co-precipitation in barite for a range of SeO42- concentrations (0–~8650 mg/L), as well as its release at near neutral pH conditions (pH = ~5.5–6.5). Solid precipitates were characterized via X-ray diffraction and subsequent Rietveld refinements, Raman spectroscopy, Brunauer-Emmett-Teller surface area analyses, scanning electron microscopy, electron probe microanalyses (EPMA), inductively coupled plasma optical emission spectroscopy (ICP-OES), and X-ray absorption spectroscopy (XAS). ICP-OES results suggested barite efficiently removed >99% of SeO42- from the test solutions during all co-precipitation experiments. EPMA results showed the SeO42- was sequestered from the aqueous phase via co-precipitation with barite. XAS analyses indicated the SeO42- tetrahedron is incorporated into the barite structure by substituting for sulfate (SO42-) and bonding to Ba2+ atoms through bidentate mononuclear and bidentate binuclear complexes. Dissolution data showed the release of SeO42- sequestered in barite to the aqueous phase is unlikely due to the low solubility and stability of the barite phase. As such, co-precipitation of SeO42- with barite could be effective for removing SeO42- from waters affected by mining and metallurgical operations.