Abstract In this paper we report new data on the occurrence and range of seven mammal species in the rainforest region of south-eastern Nigeria. The species in question are: Potamogale velox (Insectivora), Cercopithecus sclateri, Procolobus badius epieni (Primates), Manis tetradactyla (Pholidota), Funisciurus pyrropus talboti (Rodentia), Trichechus senegalensis (Sirenia) and Tragelaphus spekii gratus (Artiodactyla). In terms of conservation (according to latest IUCN criteria and categories), we discovered some critical information concerning the mammal fauna in the area. In fact, out of these seven species, one is Critically Endangered (CR), four are Endangered (EN), one is Lower Risk, least concern (LR, lc), and one is Not Evaluated (NE). Deforestation and excessive hunting pressure are the biggest threats for mammals in the Niger Delta. In particular, endemic taxa and species whose range and status are unknown, could be particularly endangered.