Due to their relatively long lifespans and large blubber stores, local sentinel species such as apex marine mammals serve as excellent models for monitoring lipophilic, bioaccumulative, and persistent organic contaminants as they become present in marine foods webs. Archived samples can also be analyzed to evaluate temporal and geographic trends. Therefore, selecting ideal messenger species for contaminant monitoring is a priority for retrospective, current, and future screening efforts. The Southern California Bight hosts notably biodiverse coastal and pelagic habitats that support a multitude of potential indicator species. A full inventory of anthropogenic and naturally occurring HOCs was generated from five full-depth blubber samples from each of five marine mammal species (long-beaked common dolphins; Delphinus capensis, short-beaked common dolphins; Delphinus delphis, Risso’s dolphins; Grampus griseus, California sea lions; Zalophus californianus, and Pacific harbor seals; Phoca vitulina) using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS). Cetaceans were found to accumulate substantially more numerous and diverse structural classes than the pinnipeds, including DDT-related compounds, polychlorinated biphenyls, and polybrominated diphenyl ethers. The common dolphin species proved to be the most effective sentinels for HOC monitoring in the Southern California Bight based upon the multitude of compounds accumulated per sample and the magnitude of contaminantabundance. Results indicate that long-beaked common dolphins are most informative for retrospective studies, whereas their short-beaked counterparts are ideal for current and future assessments based upon the availability of archived samples. The cetaceannon-targeted profiles also displayed higher amounts of halogenated natural products and unknown compounds compared to the profiles of pinniped species. The detection of these largely uninvestigated and previously unidentified contaminants aid in the identification of emerging contaminants before they become an ecological threat, allowing researchers and managers to take a proactive approach to environmental monitoring.