This study examines species composition, diversity and plant community distribution along environmental gradients of Tulu Lafto Forest (here after called TLF) in Horo Guduru Wollega Zone of Oromia National Regional State, western Ethiopia. Seventy-five quadrats of 400 m(2) were systematically laid following altitudinal gradient. A complete list of trees, shrubs, lianas and herbs including vascular epiphytes were made from each quadrat. Environmental variables including soil samples were collected, recorded and analyzed for each quadrat. In the forest, 230 plant species belonging to 188 genera and 79 families were identified. Out of these, 16 species are endemic to the flora of Ethiopia and Eritrea and 56 were new records for Wollega (WG) floristic region. Asteraceae and Fabaceae are the top species rich plant families. Cluster analysis and ordination methods identified 3 plant community types mainly influenced by topographic, edaphic and anthropogenic factors. TLF exhibited an intermediate Afromontane type suggesting the need to revise the existing vegetation classification in the country.