We undertook ethnobotanical study of forage/fodder plant species used by the Afar and Oromo (Kereyu and Ittu) Nations in and around the semi-arid Awash National Park (ANP), Ethiopia. The study aimed at investigating and documenting indigenous knowledge (IK) on forage/fodder plant species and threats to their survival. Ninety-six informants between 20 and 80 years old were selected using prior information. Data were collected using semi-structured interview, guided field walk, discussion and field observation. Preference ranking, Jaccard’s coefficient of similarity and priority ranking were used for data analysis. One hundred twenty-six forage/fodder species of 90 genera and 43 families were collected in the study area. More than 88% of the species were reported with their vernacular names, where 68% were reported by the Afar Nation and 70% by the Oromo Nation. Family Poaceae was represented by 25 species (20%), followed by Fabaceae 18 (14%). Preference ranking for the most preferred forage grasses as perceived by key informants revealed that Chrysopogon plumulosus was the most important forage/fodder species. Overgrazing was the major threat in the study area, scoring 22%.