Although the modern lesser panda (Ailurus; Ailuridae; Carnivora; Mammalia) only lives in the temperate highland forests of the southern Himalayan region, its fossil remains of late Miocene to Pliocene age have been found widely across the Holoarctic region. Very few mandibles or lower teeth of these animals, however, have been identified. Here, we provide a detailed description of the mandible and lower dentition of a large-sized lesser panda, Parailurus baikalicus (Sotnikova, 2008), which has been discovered from the middle Pliocene of Udunga, Transbaikalia, Russia. In the Transbaikalian species, lower molars are low crowned and shows highly crenulated enamel pattern. The main cuspids of cheek teeth are heavily worn horizontally, suggesting a high specialization for leaf eating. The distinctive lower tooth morphology of P. baikalicus differs from those of other fossil lesser pandas discovered from Europe and North America and from those of modern species, suggesting that the morphology found in P. baikalicus is derived in the Ailuridae.