A rapid assessment of Mt Namba recorded 271 plant taxa including six new records for Angola and 22 new records for the province of Cuanza-Sul. The mountain has the most extensive tracts of intact Afromontane forest in the country amid a mosaic of species-rich montane rocky grassland and miombo woodland at lower elevations. Range extensions of two shrubby species of Compositae reveal floristic affinities with the discrete elevated escarpment to the west of Lubango in Huíla Province nearly 400 km south of Mt Namba. We suggest that the largely intact ecological units we observed on Mt Namba might inform speculation as to the potential vegetation of the Serra da Chela which, due to local population pressures, is now mostly devoid of woody vegetation. The extent of threatened Afromontane forest vegetation in Angola and the presence of local endemic Barleria namba described from the mountain, qualify Mt Namba as an Important Plant Area for Angola. It has already been designated an Important Bird Area for the country. Araujia sericifera, an alien species of conservation concern due to its potential as an invasive, is recorded from Angola for the first time. Keywords: Angola, endemism, floristic diversity, highland, Important Bird Area, Important Plant Area, invasive plants, Mt Namba.