Ethiopian communities highly depend on local plant resources to secure their subsistence and health. Local tree resources are exploited and used intensively for medicinal purposes. This study provides insight into the medicinal importance of Hagenia abyssinica as well as the degree of threat on its population. An ethnobotanical study was carried out to document medicinal uses of Hagenia abyssinica by rural communities of North and Southeastern Ethiopia. The study was conducted using an integrated approach of group discussions, observation, a local market survey and interviews. A total of 90 people were interviewed among whom elderly and traditional healers were the key informants. Societies in the study sites still depend on Hagenia abyssinica for medicine. All plant parts are used to treat different aliments. Tree identification, collection and utilization were different among the studied communities. In spite of its significance, interest in utilizing flowers of Hagenia abyssinica as an anthelmintic seems to be diminishing, notably among young people. This is partly because the medicine can be harmful when it is taken in large quantities. Nowadays, the widely used Hagenia abyssinica is endangered primarily due to various anthropogenic impacts. This in turn may become a threat for the associated knowledge. It is recommended to assist communities in documenting their traditional knowledge. Measures for conserving species are urgently needed.