Paraphaeosphaeria barrii, a new species of the genus found on Agavaceae, is described from leaves of Yucca schidigera collected in Baja California, Mexico. The Coniothyrium anamorph is briefly described from cultured ascospores. This species was found to be most closely related to P. conglomerata, P. filamentosa, and P. quadriseptata all of which are from Agavaceae, produce 3 or 4 septate ascospores and pigmented, non-septate conidia from holoblastic, percurrently proliferating conidiogenous cells.