In this document we describe a method developed to quantify persistent organic pollutants (POPs) in-cluding polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in dietary sup-plements using stir bar sorptive extraction (SBSE)-GCMS/MS-isotope dilution mass spectrometry (IDMS). This method enables accurate, precise, and sensitive quantification of POPs in plant-extract based dietary supplement products commercially available in the United States. When compared with calibration curves, IDMS provided more accurate and precise measurements. The mean error of measurements using this method was 7.24% with a mean RSD of 8.26%. The application of GC-MS/MS enabled approximately two-order-of-magnitude lower limits of quantification compared with GC-MS. Twelve commercially available plant-extract based dietary supplement samples were analyzed using this method. PAHs including naphthalene, acenaphthene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, and benzo[a]pyrene were found in most of the products and had average concentrations over 1 ng/g. OCPs were detected less frequently than PAHs in these products, and none of the OCPs had mean concentrations over 1 ng/g. These results were compared with existing guidelines and none of the analytes in the samples were found to be above the daily allowable limits.