New excavations in the Tagay locality have revealed the presence of Amphilagus plicadentis Erbajeva, 2013, which belongs to the palaeolagine Lagomorpha rather than leporids, previously referred to Procaprolagus sp. (Logachev et al., 1964). Herein, we report a comprehensive morphological description of this species and compare it with the other known species of the genus Amphilagus. The Tagay lagomorph is conspecific with the Early Miocene species Amphilagus plicadentis found at locality Unkheltseg (UNCH-A) (biozone D; Early Miocene) in the Valley of Lakes, Central Mongolia. The Tagay specimens suggest a more advanced evolutionary stage of A. plicadentis and an age around Early/Middle Miocene transition.