North American river otters (Lontra canadensis) play a vital role in aquatic ecosystems, however, their populations are vulnerable to various environmental threats, including contaminants that may impact their health and, by extension, the health of aquatic ecosystems. The goal of this study was to determine if river otters are exposed to anticoagulant rodenticides, insecticides, and heavy metals. We performed necropsies on 20 river otter carcasses collected from the Sacramento and San Joaquin River Delta from May 2019 - December 2022. Trace exposures to anticoagulant rodenticides were detected in 45% of the tested river otters (9/20). We detected lead exposure in 10% (2/20) and mercury in 65% (13/20) of tested river otters. Trace levels of fipronil sulfone, the metabolite of fipronil, were detected in 20% of tested river otters (4/20). Other insecticides, such as organophosphorus, neonicotinoids, and pyrethrins, were not detected. While larger sample sizes and regionally specific sampling areas may help create baseline “normative” values, these results suggest that river otters in the Sacramento-San Joaquin Delta are not uniquely exposed to certain classes of pesticides that were tested for. However, the metabolic half-life of pesticides varies and may no longer be detectable in tissues by the time carcasses are collected.