A new species of praying mantis, Vates phoenix sp. nov. (Mantidae, Vatinae), is described from localities within Rio de Janeiro and São Paulo states, Brazil. This is the first record of Vates from the Atlantic Rainforest biome. The new species is unique among its congeners in having, among other features, strongly reduced cuticular projections above the lateral ocelli, structures otherwise well developed and produced in all other species of Vates. Remarks on the natural history and biogeography of Vates, in relation to this new finding, are further discussed.