Estuaries are highly productive habitats that support fisheries production. However, the importance of mangrove carbon to estuarine consumers can differ considerably among systems. In this study, we used stable isotopes (δ13C, δ15N) to investigate the importance of mangrove carbon as an energy source to estuarine consumers in the Atrato River Delta, Colombia, an area where fringing mangroves dominate the coastline and where other productive coastal habitats that may otherwise support the food web are absent. Basal resources and consumers were collected from mangrove and nearshore habitats during the rainy season. Results revealed a food web with a maximum length of 4.6 trophic positions. Bayesian mixing models indicated that most consumers used a mixture of basal sources, which suggests intertwined energetic pathways. However, mixing models also indicated that some species relied more heavily on some basal sources than others and revealed trophic pathways (food chains). Mangrove carbon directly supported herbivorous crabs (Sesarmidae) and indirectly supported planktivorous fish (Engraulidae) and piscivorous fish. Mangrove carbon also contributed significantly to the diet of 2 of the most common fish species in the local artisanal fishery: Centropomus undecimalis (mean: 46%; credibility interval [CI]: 1-80%) and C. pectinatus (mean: 33%; CI: 1-78%). Our findings highlight that mangrove carbon can be an important food source in areas without other productive coastal habitats and can play an important role in sustaining the production of fisheries.