The coordination and speciation of selenate (SeO4) and sulfate (SO4) on goethite and Al oxide were studied using Raman and ATR-FTIR spectroscopy. Raman spectra were collected from pastes of suspensions containing 4 mM SeO4 or SO4. For SO4, complementary data were collected by ATR-FTIR spectroscopy in goethite systems with 1 mM SO4 and in Al oxide systems with 4 mM SO4. The combined data set of Raman and ATR-FTIR spectra indicate that both inner- and outer-sphere surface complexes of SeO4 and SO4 occur on these metal (hydr)oxide surfaces. These spectral data show that SeO4 and SO4 have a similar complexation behavior on the same adsorbent. On goethite, these form predominantly monodentate inner-sphere surface complexes at pH <6, while at pH >6 these anions exist predominantly as outer-sphere surface complexes. On Al oxide, in contrast, these anions exist predominantly as outer-sphere surface complexes, but a small fraction is also present as an inner-sphere complex at pH <6. A comparison of the spectral intensities of these anions on goethite and Al oxide shows that complexation of these anions with Al oxide is weaker than with Fe oxide.