Different nanoclay mixing strategies using a three-roll mill and ultrasonication is proposed to obtain the desired polyester/nanoclay dispersion, intercalation, and exfoliation. The dispersion states of the modified nanoclay in polymer with 2, 4 and 6 wt% loading were characterized with X-ray diffraction, scanning electron microscopy (SEM), and low and high magnification transmission electron microscopy (TEM). The mechanical properties of the clay-reinforced polyester nanocomposites were a function of the nature and the content of the clay in the matrix. The nanocomposite containing 4 wt% modified Cloisite® 15A exhibits excellent improvement in modulus (by ∼51%) and tensile strength (by ∼12%) with a decrease in fracture strain (by ∼26%) and fracture energy (by ∼17%). These mechanical characteristic changes can be attributed to the dispersion, intercalation, and exfoliation of the nanoclays inside the polyester matrix.