Polypropylene (PP)/organoclay nanocomposites were prepared via a melt-mixing method through two-step melt compounding using a co-rotating intermeshing twin screw extruder. Maleic anhydride grafted polypropylene (PP-g-MA) was adopted during compounding as a compatibilizer. Structural investigations via X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed the intercalated morphology of the nanocomposites. The use of PP-g-MA led to not only good clay dispersion but also heterogeneous intercalation. Thermal degradation of the PP nanocomposites was studied by thermogravimetric analysis (TGA). Rheological properties of the PP/organoclay nanocomposites were also investigated via a rotational rheometer in which linear viscoelastic measurements were performed in oscillatory shear with small strain amplitude. Storage (G’) and loss (G”) moduli were found to be increased at all frequencies with increasing clay contents.