A new feather mite species of the genus MicrospalaxMégnin & Trouessart, 1884 (Alloptidae: Microspalacinae) is described from the Atlantic petrel, Pterodroma incerta (Schlegel, 1863), in Brazil. Males of M. atlanticus sp. nov. differ from M. pterodromaeDubinin, 1949 mostly by the wider opisthogastric shields and setae ps3 inserted at posterior third of that shield. This is the first representative of the genus described from Brazil, and the first feather mite described from a procellariiform bird in the country. A key to males of Microspalax species is presented.