Thunnus thynnus (Atlantic Bluefin Tuna) is an opportunistic generalist predator in the pelagic zone of the Atlantic Ocean. In the northwest Atlantic Ocean, Atlantic Bluefin Tuna diets are primarily based on small pelagic prey. Seabirds often prey on the same pelagic forage fish as tuna, leading to an overlap in the timing and location of both seabird and Atlantic Bluefin Tuna foraging activity and the potential for tuna–seabird interactions. Here, we present the first documented evidence of Atlantic Bluefin Tuna consuming a seabird in the Northwest Atlantic Ocean. This is the second report of Atlantic Bluefin Tuna consuming a seabird in the entire species' range. The evidence for this interaction comes from the stomach contents of a commercially harvested Atlantic Bluefin Tuna caught ∼1.6 km offshore of Newfoundland in October 2022. The unknown bird in the Atlantic Bluefin Tuna stomach was identified through DNA metabarcoding as Fratercula arctica (Atlantic Puffin), a diving seabird for which an overlap with pelagic predatory fish is credible. While rarely observed, it is important to identify such interactions between seabirds and predatory fish to gain a more complete understanding of food-web interactions in marine pelagic ecosystems.