Nanocomposites of polyamide six (PA6) reinforced with organoclay were prepared in this study through melt mixing. The blended montmorillonite clay was organically modified with octadecylamine. The loadings of the clay were 1 wt%, 5 wt%, and 9 wt%. The obtained nanocomposites exhibited exfoliation (1 wt%) and intercalation (other compositions) structures. By contrast, if they were mixed with unmodified clay, the PA6 molecules could not enter the silicate interlayer. For polypropylene (PP), forming nanocomposites with organoclay was difficult but made feasible by incorporating the maleated PP. The results of dynamic rheological tests demonstrated that an end-tethered storage modulus was observed for the PA6/organoclay nanocomposites. However, the PP/organoclay exhibited terminal-zone behavior. In addition, the shear creep recovery was conducted on the molten polymer composites. The results indicated that the molten PA6/organoclay nanocomposite exhibited a higher creep-recovery ratio, a measure of the elastic property, than that of pristine PA6. The time constant in the Voigt-Kelvin constitutive model for the PA6/organoclay melts was lower than that of the pristine PA6 due to the superior elastic moduli, because it is defined as the ratio of viscosity to the modulus. However, the recovery ratios for most of the PP nanocomposites were found to be less than that for the pristine PP, indicating the fair reinforcing effect of the organoclay.