The terephthalate-intercalated LDHs (TA-LDHs) are used to improve the barrier properties of poly(ethylene terephthalate) (PET) for their application in liquid food packaging. First, TA-LDHs were synthesized from freshly prepared metal hydroxides. PET/LDH nanocomposites were then prepared by a masterbatch process. The structures and morphologies of TA-LDHs and PET/LDH nanocomposites were characterized using X-ray diffractometer, transmission electronic microscopy, and scanning electron microscope. The mechanical performances and the oxygen permeability of the PET/LDH composites were measured using a precision universal tester and differential pressure gas permeameter, respectively. The influence of TA-LDH content on their structures and properties was studied. PET/LDH nanocomposites with 1 and 2 wt% of TA-LDHs are partially exfoliated nanocomposites, while PET/LDH with 5 wt% of TA-LDHs is an intercalated nanocomposite. The PET/LDH nanocomposites prepared by a masterbatch process show better mechanical properties and gas barrier properties. PET/LDHs-m2 with 2 wt% of TA-LDHs could offer up to a 29.4% improvement in tensile strength over PET and the Young's modulus is increased by 38.9%. The O-2 permeation of PET/LDHs-m2 with 2 wt% of TA-LDHs is decreased by 46.2%. POLYM. ENG. SCI., 59:E366-E371, 2019. (c) 2019 Society of Plastics Engineers