A new species of Allobates is described from the Mabura Hill Forest Reserve, central Guyana, South America. The new species is distinguished from congeneric species by cryptic colouration, very small size, first finger longer than second, third finger not distinctly swollen in males, absence of lateral fringes on fingers and toes, complete lateral black band present, diffuse pale dorsolateral stripe present, diffuse, pale, partial oblique lateral stripe present, pale ventrolateral stripe present, throat in adult males pale, and unique advertisement call and reproductive behaviour. The new species occasionally deposits tadpoles in leptodactylid foam nests, which constitutes the first case of interspecific brood parasitism in frogs. Copyright © 2007 Magnolia Press.