The effect of water on zinc-neutralized ethylene-methacrylic acid (E-MAA) ionomers and sulfonated polystyrene (SPS) ionomers was studied. The change in weight after soaking in water was quantified as a function of zinc content and correlated to changes in spectra from zinc-edge extended X-ray absorption fine structure spectroscopy (EXAFS). EXAFS patterns for the fully dried ionomers were characteristic of zinc surrounded by four oxygen atoms. E-MAA ionomers absorbed much less water per zinc atom than SPS ionomers. Addition of water changed the EXAFS pattern in E-MAA ionomers, but the pattern was still characteristic of zinc coordinated to four oxygen atoms. This change was consistent with water replacing chelating carboxylate anions coordinated to zinc at the edges of aggregates or coordinated to isolated zinc ions. A new interpretation of the v(a)(COO-) infrared vibration was developed from this work. In SPS, addition of water caused zinc to become 6-fold coordinated to oxygen, which is suggestive of zinc totally solvated by water.