We present the results of an archaeological and anthropological study of a Late Bronze Age burial at Poperechnaya-1 in the Aley steppe, Ob Plateau, south of Western Siberia. Wide-range search for parallels in the funerary rite (extended position on the left side, shallow grave pit) and burial goods (curved-backed bronze knife with ring pommel, remains of pot and meat food) demonstrates that most parallels are with Karasuk burials in the Minusinsk Basin, Southern Siberia, rather than with the local Late Bronze Age funerary tradition represented by the Irmen and Sargary-Alekseyevka cultures. The radiocarbon date of the Poperechnaya-1 burial (1500–1200 BC) corresponds to the early stage of the Karasuk culture. Craniometric analysis of the preserved part of the cranium indicates a very high and broad face with a wide nasal bridge, which agrees with cranial characteristics of the Karasuk samples from Sukhoye Ozero II and Kyurgenner I and II. The X-ray fluorescent analysis of the bronze knife revealed tin in the alloy. Similar alloys are typical of knives with ring pommels from Southern Siberia (groups 11–13 according to N.L. Chlenova’s classification) and nearly never occur in the Irmen metal artifacts. The totality of findings suggests that the burial indicates the presence of Karasuk people in south of Western Siberia in the Late Bronze Age. A higher mobility of South Siberian population during the Late Bronze Age was probably caused by the emergence of craft and trade centers near the ore sources in the Ob-Irtysh steppe and in Central Kazakhstan and by the development of trade routes during the Late Bronze Age.