The effect of ionic interactions on the crystallization behavior of lightly sulfonated syndiotactic polystyrene (SsPS) ionomers has been evaluated for systems containing 0.5 and 2.0 mol % sulfonate groups. In agreement with studies of other semicrystalline ionomers, the rate of SsPS crystallization decreases with increasing sulfonation and neutralization. For the neutralized ionomers containing 2 mol % sulfonation, the size of the alkali metal counterion was found to have a significant effect on the rate of crystallization. SsPS ionomers containing large Cs+ ions crystallized at about twice the rate of the ionomers neutralized with small K+ions. From SALS and SAXS results, isothermally crystallized SsPS ionomers were found to form spherulitic superstructures in the presence of ionic aggregates. These ionic domains were found to have an average intermultiplet spacing which is identical to that of sulfonated atactic polystyrene ionomers. In addition, wide-angle X-ray diffraction studies showed that the polymorphic crystal structures of sPS are strongly influenced by the incorporation of small quantities of ionic groups along the polymer backbone. Under isothermal crystallization conditions, the SsPS ionomers were found to preferentially organize into the beta-form crystal structure.