Numerous moderately preserved radiolarians of Tethyan affinity were extracted from a purple-red chert sample from the Luoqu Section on the southern side of the Yarlung-Tsangpo suture zone in the Xigaze area, southern Tibet. Ninety-three species belonging to 35 genera are recognized, of which one is described as Citriduma pentaptera sp. nov.; most of them are reported from Tibet for the first time. Significantly, this radiolarian assemblage of nassellarians, subordinate spumellarians and rare entactinarians can be compared with those in Oman, Japan, Oregon and Queen Charlotte Islands and is further assigned to the Eucyrtidiellum nagaiae-Praeparvicingula tlellensis zone of late Pliensbachian in age. This indicates that the pelagic deposits of the Neo-Tethys Ocean in the Xialu area were laid down at least during or since the late Pliensbachian, much earlier than the Aalenian age previously considered.