Nanocomposites were prepared by melt blending a series of sodium ionomers formed from poly(ethylene-co-methacrylic acid) and the M-2(HT)(2) organoclay. The effects of the degree of neutralization of the acid groups on the morphology and properties of the nanocomposites were evaluated using stress-strain analysis, wide-angle X-ray scattering (WAXS), and transmission electron microscopy coupled with particle analysis. The organoclay exfoliation improves progressively as the neutralization level of the sodium ionomers increases. It seems that the ionic units on polymer chains provide a more favorable interaction between the polymer matrix and organoclay than acid units. Predictions of the tensile modulus of the nanocomposites by the Halpin-Tsai equations capture some of the experimental trends, but the absolute values do not agree well with the experimental observations.