A new species, Croton uliginosus, from Midwestern Brazil is described and illustrated. It is related to Croton junceus Baill., from which it differs mainly in shape, margins and veins of leaf blade, position of acropetiolar glands, number of pistillate flowers in the rachis, presence of glands, shape of pistillate sepals, number of stamens, and length of fruiting pistillate calyx in relation to the fruits. The habitat, preliminary conservation assessment, periods of flowering and fruiting, and morphological relationships of the novel species with its closest species are also provided. Additionally, the geographical distribution map and color plates of the new species and C. junceus are provided. The latter is a species endemic to Midwestern Brazil but not yet revealed in photographs, whose taxonomy is still poorly known.