Four new species of Mimosa are described and illustrated: M. kalunga, M. pseudosetosa, M. viperina, and M. diminuta (all from section Habbasia, series Pachycarpae). All of them are apparently narrowly restricted endemics from the Chapada dos Veadeiros in Goiás, central Brazil. In addition, more complete data and an illustration are presented for M. pycnocoma Benth., previously incompletely known only from the type collection. The new species described here, as well as the new data on M. pycnocoma, provide interim increments to our knowledge of a group of around 55 Mimosa species, combining Barneby's (1991) series Setosae and Pachycarpae, that remains poorly and incompletely understood.