The Carajás National Forest is located in the Amazonian region, Pará State, Brazil and is part of a mosaic of conservation units comprising over one million hectares. This region has been explored for its mineral reserves, but knowledge of the distribution of animals and plants is lacking. The objective of this paper is to provide a list of the medium and large-sized mammals recorded from the Carajás NF. We used four methods to record mammals: linear transects, camera traps, records of road-killed animals, and opportunistic observations. We recorded 45 species distributed in nine taxonomic orders, eight of them currently on the Brazilian list of threatened species and seven in the IUCN red list. The area has high mammalian diversity and holds 56% of the threatened species known for the State, confirming that the study area is correctly categorized as Extremely High Priority for the conservation of Brazilian biodiversity.