According to professors Bozena Werbart and Jonathan Shepard, the Tengri "sun-amulets" disappeared after the 830s from Khazarian graves, as did other shamanistic possessions, indicating a dramatic shift in religion in the Khazar kaganate.

This is a highly controversial question, based upon contradictory information from various primary sources. The earliest possible date is Yehuda HaLevi's estimate of 740. Abd-al-Jabbar al-Hamdani and other Middle Eastern writers claim the conversion happened during the reign of the Abbasids. Al-Masudi would have us believe that the conversion took place sometime between 786 and 809.

But according to Constantine Zuckerman of the Collège de France (Paris), the Khazars' conversion to Judaism probably took place in the 9th century rather than in the 8th century. This argument has also been taken up by Jonathan Shepard and Kevin Brook, who state that the first record of Khazarian Judaism dates only to about the year 864, and that the Byzantine missionaries Cyril and Methodius upon their arrival in Khazaria in 860 approached and debated with a people whom had not yet adopted full Judaism. It used to be argued that the Khazars could not have sincerely adopted Judaism if they still had good relations with the Christian Byzantines even in the late 8th century. But historical analysis cancels this argument by showing that the decline in the Byzantine-Khazar relationship is tied directly to the time of the Khazar conversion to Judaism, and may be dated as occurring sometime during or after the 830s. A conversion date in the mid-to-late 830s is supported now also by the Moses coin (discussed below) which dates from 837-838, whereas just a few years earlier (around 834) the Khazars and Byzantines were cooperating on building Sarkel.

According to Thomas Noonan of the University of Minnesota, in his article "The Khazar Economy" [Archivum Eurasiae Medii Aevi 9 (1995-1997): 253-318], the Khazar civilization is rich in material remains, and contributed to the medieval world economy. Excavators continue to find artwork, pottery, and other artifacts produced by the Khazars. This evidence appears to contradict the opinions of Ananiasz Zajaczkowski, Douglas Dunlop, Francis Dvornik, and others that the Khazars were merely middlemen and not producers of quality goods.