© 2022 John Wiley & Sons Ltd.This study deals with the improvement of light barrier properties and stress cracking strength of polyethylene terephthalate (PET) packaging materials by incorporating calcium metaborate (CaB2O4). CaB2O4 powders were synthesized by the sol–gel method. After the extrusion process produced PET/ CaB2O4 granules, the preform and bottle production was carried out by injection molding and blow molding. Compared to pure PET, UV transmittance is reduced (~88%), and it is more effective at lower wavelengths (<800 nm). Similarly, the presence of CaB2O4 improved the environmental stress cracking performance of PET packaging materials. While the burst strength increased in the range of 0.05%–0.2% CaB2O4 concentration, it decreased at higher concentrations. The load-carrying capacity is approximately 109% higher than pure PET. Acetic acid (COOH) degradation increased with the incorporation of CaB2O4 particles, while isophthalic acid and diethylene glycol degradations did not change. The experimental data indicate that the photocatalytic degradation of the PET bottle is prevented significantly, and its mechanical performance is also improved with the incorporation of CaB2O4. Thanks to this novel product, the quality of food and beverages in PET packaging materials can be protected from the harmful effects of light, and the deformation of PET packaging materials can be prevented for various reasons.