Kermadec petrels (Pterodroma neglecta) are shown to be resident in the Atlantic Ocean, breeding at Ilha da Trindade, off Brazil, South Atlantic Ocean and migrating to the North Atlantic. Previously mistaken for Trindade petrels (Pterodroma arminjoniana) at Ilha da Trindade, they were identified by the whitish shafts and largely white inner webs of their primaries and, at the colony, by their distinctive call. Records of five non-breeding Kermadec petrels in the North Atlantic Ocean include the first Atlantic specimen from western United Kingdom in 1908. All of eight identifications of Kermadec petrels from Atlantic waters were dark phase birds, like those identified from the Indian Ocean, though, in the Pacific Ocean, the species is polymorphic. Trindade petrels from Ilha da Trindade are mostly the light phase (59%, n = 71), outnumber Kermadec petrels there by about 20:1 in collections, and disperse into the North Atlantic Ocean. As 70% (n = 43) of these two species combined observed at sea in the North Atlantic were dark phase, about 49% of North Atlantic records may have been Kermadec petrels. As they are in Pacific waters, Kermadec petrels may be more migratory and reach higher latitudes than do Trindade petrels. The Halipeurus feather louse hosted by Kermadec petrels in the Pacific Ocean has been identified from both petrels in Atlantic waters, but that hosted by Trindade petrels elsewhere has not been reported from Atlantic waters, possibly indicating earliest colonisation by Kermadec petrels. The morphometrics of Trindade petrels in the Atlantic Ocean cannot be established accurately until the generally larger Kermadec petrels are excluded from data sets.