Na-23 nuclear magnetic resonance (NMR) is used to observe the sodium cations in sulfonated polystyrene ionomers (NaSPS). Three NMR peaks are detected, corresponding to isolated ion pairs, aggregated ions, and hydrated ions. Peak intensities vary with sample composition and treatment and provide insight into the effects of these variables on the morphology of the ionomer. Ion distributions are systematically influenced by hydration treatment, sulfonation level, and neutralization level. Fully dried NaSPS at low ion content shows isolated and aggregated sodium ions. Once humidified, the single peak at 0 ppm characteristic of fully hydrated sodium ions indicates that all sodium ions in NaSPS are available for hydration. As the sulfonation level increases, the fraction of sodium ions held in isolated ion pairs decreases while the fraction of ionic species in aggregates increases. This coincides with a shift in the peak position of the aggregated sodium ions to lower frequency, indicative of increased quadrupolar interactions. Finally, as the neutralization level increases at a constant 3.4% sulfonate content, the aggregate peak shifts to higher frequency due to incorporation of the neutralizing agent, NaOH, into the aggregates. At very high neutralization levels, a separate NMR peak characteristic of phase-separated NaOH appears.