The aim of this work was to study the effect of functionalized single-walled carbon nanotubes (f-SWCNTs) on the microstructure of PP-g-MA/organic modified montmorillonite (OMMT)/f-SWCNTs ternary, nanocomposite. Pristine SWCNTs were chemically modified by maleic anhydride to improve,e the interaction between PP-g-MA and nanotubes. The dispersion states of OMMT in the different nanocomposites were investigated by wide angle X-ray diffraction. The morphologies scanning of the nanocomposites were characterized by electron microscopy. Crystallization behaviors of nanocomposites were studied through differential scanning calorimetry and polarizing optical microscopy. Different than the PP-g-MA/OMMT binary nanocomposite, in which the OMMT is mainly in all exfoliated state, the ternary PP-g-MA/OMMT/f-SWCNTs nanocomposite exhibits mostly intercalated OMMT. Furthermore, in the ternary nanocomposite, the crystallization of polymer is mainly induced by f-SWCNTs rather than by OMMT. (C) 2009 Wiley Periodicals, Inc, J Appl Polym in Sci 112: 2413-2424, 2009