We describe a new species of Chiasmocleis from the municipality of Una, in the Atlantic Rainforest of southern Bahia, northeastern Brazil. The new species is the smallest member of the genus and is characterized by having an ovoid body; a truncate snout in dorsal view, rounded snout in profile; no webbing on hands and feet; fingers lacking disks, toe tips slightly expanded; fingers and toes weakly fringed (less fringed in females), with few lateral dermal spines in males and none in females; the dorsal surface of body and limbs with dermal spines in males, absent in females; in preservative, color on dorsum uniformly grayish brown, paler brown on dorsal surface of limbs; posterior surface of thighs with a white, longitudinal line; and belly boldly marbled in brown and pale cream.