Gonocalyx lilliae (Ericaceae), a new species endemic to Costa Rica, is described and illustrated. This new species is somewhat similar to G. costaricensis, sharing similar shape and leaf size, racemose inflorescences, short rachis, inconspicuous bracteoles, and flowers with the hypanthium terete to subterete, with inconspicuous calyx lobes. However, G. costaricensis is separated by its glabrous leaves, flowers, and fruits; inconspicuous inflorescence bracts; and stamens with free filaments. A brief synopsis and a key to the species of the genus in Costa Rica are given.