A poly(ethylene terephthalate) (PET)/organosilicate nanocomposite, with enhanced mechanical properties, has been prepared using the melt intercalation method. For this purpose, a new organic modifier has been synthesized for the preparation of organosilicate, which is thermally stable and compatible with PET. The use of the new organosilicate yielded almost exfoliated PET nanocomposite; whereas, the PET nanocomposites prepared by use of commercial organoclays (Cloisite 15A and 30B) show only an intercalated morphology. Particularly, the use of the new organosilicate showed an enhanced tensile modulus, and without sacrifice of the tensile strength and elongation on breaking, while the use of commercial organoclays only exhibit a trade-off between those mechanical properties.