Summary: In estuarine ecosystems, terrestrial primary producers such as riparian and marsh vegetation are believed to promote resilient food webs through direct (detrital) and indirect (consumptive) pathways, but the inherent interconnectivity of estuarine systems often obscures the origins and importance of these terrestrial inputs. The goal of this study was to determine the relative contributions of terrestrial and aquatic primary producers to the estuarine food web and the pathways by which these primary sources influenced food web structure. To accomplish this, we used a Bayesian stable isotope mixing model to elucidate relationships among primary producers, invertebrates, and a pelagic and demersal fish species in the Nisqually River Delta, Washington, USA. Our findings are important for characterizing connectivity among estuarine habitat types and the means by which connectivity contributes to robust estuarine food webs.