Two new species of Tibouchina, tribe Melastomeae (Melastomataceae), are herein described, illustrated and compared with their congeners. Tibouchina bracteolata and T. comosa have dense inflorescences and pentamerous flowers, with two narrow and deciduous bracteoles, and are morphologically similar to T. regnellii Cogn. and T. nodosa Wurdack, respectively. Moreover, they can be distinguished by vegetative and floral characters, as well as by phytogeographic aspects. The two new species were found exclusively in mountainous areas of the Chapada Diamantina, Bahia, Brazil, they are endemic to this region and correlated with distinct vegetation types: ‘campo rupestre’ (T. comosa) or riparian forest (T. bracteolata). On the other hand, T. regnellii is known only to the Atlantic forest of southern Brazil, while T. nodosa occurs in the ‘cerrado’ vegetation from central and southern Brazil.