Due to the very rare mammal inventories in the northern half of the Atlantic Forest in the state of Bahia, Brazil, all initiatives to increase the knowledge of the group in this region are greatly appreciated. Thus, herein we present an inventory conducted in the privately owned Guarirú Nature Reserve, a fragment of Atlantic Forest in several conservation/regeneration stages. Sampling was carried out using Tomahawk, Sherman, and Pitfall traps over one year. The sampling resulted in 154 captures of 93 individuals from 12 different species. The didelphids Didelphis aurita, Gracilinanus microtarsus, Marmosa murina, Marmosops incanus, Metachirus nudicaudatus, Micoureus paraguayanus, and Monodelphis americana were recorded, as well as the cricetids Akodon cursor, Oligoryzomys sp., and Rhipidomys sp., and the echimyids Trinomys albispinus and T. setosus. Given the relative lack of knowledge about this important portion of the Atlantic Forest this inventory is an important contribution to the mammalogy of Brazil.