Treefrogs of the genus Boophis comprise the most species-rich genus among all Malagasy frogs. In this paper we describe a new species to be added to this genus from Masoala Peninsula and nearby areas. Related populations have been found in three localities of North-Eastern Madagascar (Tsararano, Marojejy, and Anjanaharibe-Sud), and molecular data indicate that at least the Marojejy population is strongly differentiated. The new species has an attractive pink or reddish colour pattern on a green ground colour. It bears a strong similarity to Boophis bottae and B. rappiodes in morphological appearance, but is genetically very distinct from these and other members of the Boophis rappiodes group. Boophis ulftunni sp. n. belongs into a separate evolutionary lineage probably related to the Boophis microtympanum group, a lineage of highland species from Central Eastern Madagascar which otherwise have very different phenotypes and advertisement calls. We here include B. ulftunni in a new phenetic species group, the Boophis ulftunni group.