The article presents the publication of inlet burial of horse dated by Mongolian time, which was excavated by S.S. Sorokin at the Pazyryk complex in 1967. Based on the archival materials, the museum collection from the State Hermitage and publications, a general description of the “ritual” mound №21 is presented. It is established that this object is located in the southern part of the famous burial ground, not far from “royal” burial mound №5 of the Scythian-Saka time. Under the central part of the embankment at a shallow depth was the inlet burial of a horse oriented in a western direction. Iron teeth with ringed psalia were found in the teeth of the animal. Analysis of excavation materials of the inlet grave allowed us to justify the dating of the object and to present the possibilities of its interpretation. The existing extensive analogies, along with the consideration of general trends in the development of horse equipment, give grounds to conclude that the complex under consideration belongs to the Mongolian time and can be dated within the 13th – 14th centuries AD. The information obtained about the burial rite widens the existing understanding of the traditions of the Altai population during the developed Middle Ages. In particular, the received materials confirm the existence in Altai in the Mongolian time of the tradition of creating “separate” burials of horses, during the construction of which special ritual actions could have been carried out.