The effects of the incorporation of multiwalled carbon nanotubes (MWNT) with a diameter range of 10-30 nm on the shear-induced crystallization behavior of poly(butylene terephthalate) (PBT) were investigated under myriad shearing and loading conditions employing principally the small-amplitude oscillatory shear flow. Upon shearing, the presence of MWNTs leads to the crystallization of the PBT nanocomposites at temperatures that are higher than the crystallization temperature of unfilled PBT. The Avrami analysis of the shear-induced crystallization data of PBT nanocomposite samples indicated that the kinetics of the crystallization depend on both the temperature and the concentration of the MWNTs. When the MWNTs were replaced with similar to 70 mu m graphite particles at similar volume loading levels the crystallization behavior of the PBT/graphite suspension samples did not differ from that of pure PBT. These findings emphasize that one primary mechanism associated with the significant changes in the mechanical properties observed upon the compounding of nanoparticles into various semicrystalline polymers is the change in the crystallization behavior of the polymer as affected by the presence and the concentration of the nanoparticles and the associated changes in the microstructural distributions of the nanocomposite.