Cardiospermum bahianum, a new species from Bahia, Brazil, is described, illustrated, and compared to its putative closest relatives C. anomalum and C. cuchujaquense. The new species is endemic to the caatinga vegetation. In addition, micromorphological characters of leaf epidermis, seed coat, and pollen grains are described. A somatic chromosome number of 2n = 36 is reported. Detailed light and scanning electron microscope photographs of the main characters are presented. The new species belongs to Cardiospermum section Carphospermum. It is distinguished from the similar C. anomalum by its conspicuous lenticels, seeds nearly spherical, and it differs in chromosome number. Additionally, new synonymies for C. anomalum are established. A key to the species of Cardiospermum in Brazil is provided.