Polyethylene terephthalate (PET) is commonly used in beverage packaging and can be recycled to reduce plastic pollution, raising concerns regarding non-intentionally added substances (NIAS). Here, two organic NIAS, acetaldehyde and benzene, and metal elements have been examined in PET materials. Elemental analysis revealed that higher recycled content in PET correlated with increased contaminant levels. Moreover, elevated acetaldehyde and benzene concentrations were noticed. PET degradation, intentional addition, and unknown sources complicate the analysis of the effects of the production, recycling, and storage on the introduction, formation, or migration of NIAS in PET materials. Benzene and acetaldehyde could migrate into beverages or the environment during storage. The migration of these two volatile substances was therefore quantified. Despite their presence in all PET materials, the low concentrations of acetaldehyde and benzene detected alleviate potential health concerns. This research contributes to the understanding of how recycling and recycled content impact the presence of NIAS in PET, offering insights for optimizing recycling practices and sustaining the role of PET in environmentally responsible beverage packaging.