Persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs), dichlorodiphenyl trichloreothane (DDTs), polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) are toxic nonpolar molecules that can cause damage to the reproductive, developmental, behavioral, and endocrine systems. These pollutants accumulate within the fatty tissues of important species in Puget Sound, including orca whales, salmon, herring, and plankton. This study measured the concentrations of two banned POPs, PCBs and PBDEs, and one currently used POP, HBCD, in plankton communities in Possession Sound. POP concentration in the water was measured in situ using a Chemcatcher deployment device to passively sample water at five locations across Possession Sound. Gas chromatography-mass spectrometry (GC-MS) was used to identify and quantify the POPs collected on the Chemcatcher filters and in the plankton samples. This two-pronged approach to sample both the water and plankton communities helps better define the relationship between POP concentrations in the water and those in the plankton community. This relationship is critical as plankton serve as the primary entry point for POPs into marine food webs. Additional research is needed to help determine the pathways that these pollutants travel between organisms.