Persistent organic pollutants were assessed in Humboldt Penguins ( Spheniscus humboldti) from the Punta San Juan Marine Protected Area, Peru, in the austral winter of 2009. Plasma samples from 29 penguins were evaluated for 31 polychlorinated biphenyl (PCB) congeners and 11 organochlorine pesticides (OCPs) by using gas chromatography coupled to an ion trap mass spectrometer and for 15 polybrominated diphenyl ether (PBDE) congeners by using gas chromatography coupled with high-resolution mass spectrometry. The detection rate for PCBs in the samples was 69%, with congeners 105, 118, 180, and 153 most commonly detected. The maximum ΣPCB concentration was 25 ng/g. The detection rate for DDT, DDD, and/or DDE was higher than for other OCP residues (90%; maximum concentration=10 ng/g). The detection rate for PBDEs was 86%, but most concentrations were low (maximum ΣPBDE concentration=3.81 ng/g). This crucial breeding population of S. humboldti was not exposed to contaminants at levels detrimental to health and reproductive success; however, the identified concentrations of legacy and recently emerged toxicants underscore the need for temporal monitoring and diligence to protect this endangered species in the face of regional human population and industrial growth. These results also provide key reference values for spatial comparisons throughout the range of this species.