The 65 Ma Chicxulub impact is known to have triggered large submarine slope failures near the crater in the Gulf of Mexico and Caribbean. Here we show that the impact also precipitated massive submarine failure of the continental margin around the western North Atlantic. We have identified mass-flow deposits containing impact ejecta of Cretaceous-Paleogene boundary age in two deep-sea cores more than 700 km from the continental margin. The mass flows must have originated from the continental margin because they contain microfossils typical of shallow-water environments and sedimentary features indicative of deposition by gravity currents. Geophysical data suggest that the mass-wasting deposits may be present over the entire western North Atlantic from Puerto Rico to the Grand Banks of Canada, and that much of the eastern margin of North America catastrophically failed during the Cretaceous-Paleogene impact.