This article considers the process and results of the formation of the social group made up by the Yedinovertsy priests in the Don and Novocherkassk Diocese. Based on the analysis of the sources, it is shown that 27 Yedinovertsy churches had been established in the territory of the Don Army Land by the 1910s, which resulted from the development of the missionary movement that was expected to prevail over the Old Believers’ schism. It was initiated by hierarchy of the Don region, diocesan missionaries, and some Old Believers who had joined the Russian Church under the Old Believers’ “rules”. A group of priests was formed to provide service in those churches. The priests were familiar with the rites that were forbidden in 1666-1667 and wanted to perform their missionary activities among the Old Believers. At the beginning of the group formation process, in the Yedinovertsy churches, there were only 29 priests and psalm readers, who did not have the required education level. But by 1910, their number had grown up to 55 clergymen. Not only did they know the old rites well enough, which, in some instances, was caused by the fact that they had come to the Russian Church from various schism branches, they were also of the advantageous Cossack origin and had missionary education received from the Don diocesan missionary school specially established for those purposes. Considering how important the Yedinovertsy priests’ service was both for the management of the Diocese and the Don Army, those organizations were the financing sources for the priests, for the churches themselves did not even provide the Yedinovertsy priests and psalm readers with an average income. The integrity of the social group in question was sustained by the fact that priests serving at Yedinovertsy churches seldom moved to serve at Orthodox temples.