Technical Abstract: Most analytical methods for persistent organic pollutants (POPs) focus on targeted analytes. Therefore, analysis of multiple classes of POPs typically entails several sample preparations, fractionations, and injections, whereas other chemicals of possible interest are neglected. To analyze a wider scope of organic contaminants in fish oil, we developed an untargeted screening approach using comprehensive two-dimensional gas chromatography with time of flight mass spectrometry (GC×GC/TOF-MS) and direct sample introduction (DSI). The novel approach incorporated a simple sample preparation procedure merely using gel permeation chromatography (GPC) for clean-up of dietary cod liver oil, which provided a wide analytical range of targeted and untargeted chemicals in the same method. Not only could the method quantify and identify several classes of POPs in the samples, but it could also make presumptive identifications of numerous halogenated natural products (HNPs) by comparisons of the mass spectra from analyses with those from mass spectral libraries and/or reports in the literature. Subsequent confirmations were made when possible by re-analysis and comparison of chromatographic retention times and mass spectra with contemporaneously analyzed reference standards. In this paper, ion fragmentation patterns of unusually detected compounds and their sources are discussed. For the first time, several groups of HNPs were identified in cod liver oil at the same time.