Contamination in food from packing material can occur in trace quantities. However, the migration of substances from food packing material needs to be evaluated to ensure that the levels are not toxic. Terephthalic acid (TA) can migrate into mineral water stored in polyethylene terephthalate (PET) bottles and pose a wide range of health hazards depending on the toxicological threshold. A magnetic dispersive micro solid-phase extraction (MDMSPE) associated with HPLC–UV was implemented to determine TA levels in mineral water from PET bottles. The calibration curve was constructed with the correlation coefficient up to 0.99 over the concentration range of 50–500 ng/mL. The recoveries ranged from 98 to 105% and the relative standard deviation (RSD) and accuracy was < 8%. This method is quick, sensitive, simple and accurate, and could be applied to determine TA in water stored in PET bottles in a short analysis time.