Abstract Mammals function as ecological engineers. The ecological relevance of mammals, shortage of data and increased human threats make the matter very essential and necessary to evaluate their diversity and current conservation status. Mammals’ diversity and their threats in Faragosa Communal Forest (FCF) areas are poorly surveyed. The study aimed at assessing medium and large-sized mammals of the study area, and their major threats in FCF. Survey of mammals conducted from August to December 2019 in FCF, Gamo zone, Southern Ethiopia. Transect line method using direct and indirect field observations used to collect data on mammals and their threats. A total of 685 individuals were id belonging to twenty-one mammalian species, six orders and thirteen families were observed. Hystrix cristata, Xerus rutilus, Marmota monax, Mellivera capensis, Chlorocebus aethiops, Papio anubis, Colobus guereza, Civettictis civetta, and Lapus hassinicus were among the medium-sized mammals while Tragelaphus imberbis, Redunca redunca, Ourebia ourebi, Sylvicapra grimmia, Phacochoerus aethiopicus, Pontamochoreus larvatus, Hippopothamus amphibus, Orycteropus afer, Crocuta crocuta, Panthera leo, Panthera pardus, and Canis mesomelas were the large mammals of the study area. Papio anubis and Chlorocebus aethiops were the dominant species identified. The abundant order recorded by the number of observations was order Primates (284 individuals) followed by order Artiodactyla (201 individuals) while the least abundant order was Tubulidentata (8 individuals). Among observed 685 mammals, 371 (54.16%) individuals were recorded in dry season while 314 (45.84%) individuals were recorded in wet season and abundance significantly varied between seasons (2 = 40.783; df = 20; < 0.05). The prevailing threatening factors identified were logging of trees for fuelwood and house construction, overgrazing, deforestation, hunting, mining, and invasive alien plants. As the area is rich in mammals and threatened by different factors, urgent conservation action is highly recommended. K E Y W O R D S diversity, Ethiopia, Faragosa forest, mammals, threats