We describe a large new species of leaf-tailed gecko endemic to northern Madagascar. Uroplatus garamaso sp. n. is the sister species of U. henkeli but differs by a genetic divergence > 8% in the mitochondrial 16S rRNA gene, by the absence of haplotype sharing in four nuclear-encoded genes analyzed, a smaller body size, slightly narrower tail, a more pronounced yellowish/reddish iris colour in most individuals, and lack of black pigmentation on the tip of the tongue. The new species also appears to consistently differ from U. henkeli in genital morphology, with the apex of the hemipenis ending in two terminal elements consisting of 4–5 rotulae and longitudinal rows of calyces (versus an apex with irregularly distributed calyces and ending in two symmetrical structures consisting of two broader serrated fleshy elements in U. henkeli). We genetically confirm the occurrence of U. henkeli over a rather wide area, ranging from Tsingy de Bemaraha in the West to Nosy Be in the Sambirano region of northern Madagascar. Both, U. henkeli and the new species contain several deep mitochondrial lineages that are considered as conspecific due to extensive haplotype sharing and lack of obvious morphological differences among them.