The practice of traditional medicine is common in Ethiopia although it is not utterly studies and documented. So, the aim of this study is to conduct an ethnobotanical survey of medicinal plants used for treatment of human and livestock health problems in Chencha district, Gamo Gofa, Ethiopia. A cross sectional study and systematic sampling technique was employed to select potential sampling areas and medicinal practitioners between 2012 and 2013. A total of 9 sampling sites were selected, and ethnobotanical data was gathered using semi-structured interview and field observation, and analyzed using descriptive statistics, informants' consensus and fidelity level index. A total of 89 medicinal plants are discovered of which 42 species (47%) are harvested from ex-situ while 19 species (21%) are harvested from in-situ. Analysis of informants' consensus factor (miICF=0.64) shows the presence of high intra-cultural uniformity amongst practitioners in using plants for multiple purposes. So, efforts have to be made to integrate such alternative medicine with modern medicine. Sustainable conservation of medicinal plants and its associated knowledge should be implemented.