Thermoplastic and amorphous poly(ethylene terephthalate)/clay nanohybrids have been prepared through solution route. Organically modified NK75 nanoclay has been used as filler in different concentrations to enhance the properties. The Young’s modulus has increased significantly (66%) though there is slight reduction in toughness. Halpin Tsai and Hui-Shia models have been fitted well to explain the nature of stiffness for the prediction of the modulus values. Vicker hardness test has shown considerable improved hardness (16%) in nanohybrids and are nicely predicted using the modified rule of mixture model. The effect of uniaxial stretching on the structural development is explored through small angle X-ray scattering and wide angle XRD. The nanoclay has induced short range ordering upon stretching in nanohybrids as compared to pure PET. Nanoclay has induced high barrier for gas permeation in nanohybrids in comparison to pristine PET. Oxygen transmission rate has also been found to decrease up to 38% for using meager amount of nanoclay. The experimental permeability data has been fitted with different models and has been found suitable for its real applications.