A new species of Capparis L., C. irenae Fici, sp. nov., is described and illustrated from Tigapuluh Mts., Riau Province of Sumatra, where it is known from a single locality in forest communities. The new species, belonging to Capparis sect. Monostichocalyx Radlk., is related to C. diffusa Ridl., differing in several characters as the glabrous twigs, longer petioles and leaves, flowers arranged in racemes with cataphylls at the base, longer petals hairy outside and longer filaments. Its affinities with other related taxa and its conservation status are discussed. Moreover a distribution map of the new species and an identification key to the species of Capparis recognized in Sumatra are provided.