Biodiversity surveys and the compilation of indigenous knowledge were conducted in eight previously unstudied proposed and already gazetted Forest Reserves of Mtwara Region, south-eastern Tanzania, from April to August of 2005. The results indicate relatively low biodiversity and endemism values in these forests, and high levels of forest disturbance. In most areas the original vegetation has been converted by clearance for cultivation and by fire, and has regenerated into degraded forms of Swahilian/Coastal Mixed Dry Forest, Swahilian/Coastal Brachystegia Forest and floristically impoverished Zambezian-Swahilian Brachystegia Woodland. Some Coastal Forest endemic and threatened species, however, occur in the degraded forest patches, such as east coast akalat Sheppardia gunningi, Reichenow's batis Batis mixta reichenowi, spotted flat-lizard Platysaurus maculatus, woodland toad Mertensophryne micranotis and the shrub Gardenia transvenulosa. The low proportion of endemic and threatened species recorded implies that these forests are of modest biological importance within the context of the Eastern Arc Mountains and Coastal Forests Biodiversity Hotspot. Nevertheless, local inhabitants depend heavily on the long-term availability of timber and non-timber resources and water and soil regulation services from these forests. The development and implementation of effective natural resource management is therefore urgently needed in this area.