A new species of Oecanthus Serville, 1831 is described from Texas. Oecanthus walkeri n. sp. Collins & Symes occurs in southern Texas on Seep Willow (Baccharis salicipholia), Tepejuage (Leucaena iveruienta) and Sugar Hackberry (Celtis laevigata) trees. O. walkeri is currently known only from the Rio Grande Valley. Song analysis revealed a pulse pattern of constant trilling, similar to other constant trillers of the O. nigricornis species group, although the early evening calling pattern shows characteristics of the O. niveus group. This species was only found in trees, which is uncommon for the O. nigricornis group. The antennal markings are consistent with the O. nigricornis group; however, this is the first species of that group to have a pale abdomen, pedicel and scape, while also having black flagellae. Notes are provided on physical morphology, phenology, habitat and song pulse rates at given temperatures.