Sorbic acid, benzoic acid and their salts and sodium dehydroacetate are used as preservatives to prevent the alteration and degradation of foods by micro-organisms. Although several analytical methods, including a method that combines steam distillation pre-treatment and HPLC analysis, have been developed for the determination of preservatives in various processed foods, these methods require complicated and time-consuming pre-treatments to extract and/or purify the preservatives from these foods. In this study, we developed and validated a method for determining these preservative levels in various processed foods using solvent extraction and quantitative 1H NMR analysis with a certified reference material as the internal standard (IS). These preservative levels were determined by comparing their proton signals with those of the IS (DSS-d6 or 1.4-BTMSB-d4) after simple solvent extraction from processed foods. In the recovery test, all recoveries of preservatives from several processed foods spiked at two concentrations greater than 80%. In addition, the developed method proved to have intra- and inter-day precision as well as excellent linearity. Furthermore, the method was very rapid and easy to apply and provided International System of Units traceability without the need for an authentic analyte reference material. Thus, we concluded that the developed method is a useful and practical tool for determining the preservative levels in processed foods.