Lijndenia udzungwarum R.D. Stone & Q. Luke, a shrub or small tree of Tanzania’s Udzungwa Mountains, is described and illustrated. The placement of the new species in Lijndenia is indicated by its trinervate, papillose-muricate leaves and persistent bracteoles partially fused to form a cupule immediately subtending each flower. The cordate leaves of L. udzungwarum are unique in the genus. From the East African L. brenanii (A. Fern. & R. Fern.) Jacq.-Fél. and L. procteri (A. Fern. & R. Fern.) Borhidi, the new species is further distinguished by its capitellate inflorescences on long, filiform, axillary peduncles, resembling those of the Sri Lankan L. capitellata (Arn.) K. Bremer. Despite its local endemism, L. udzungwarum has been assessed as ‘Least Concern’ according to IUCN criteria, although this assessment is dependent on the continued safeguarding of the Udzungwa Mountains National Park. An identification key is provided for the three currently recognized Tanzanian species of Lijndenia.