The Sabbatarian religious movement emerged in Europe in the Modern Era. Seventh-day Sabbatarianism embraced both Christian denominations observing Sabbath and dechristianizing streams building up religious beliefs and practices on the basis of the Old Testament. Judaizing Sabbatarians included English, German, Polish, Russian and Transylvanian Sabbath keepers. The latter (Szombatosok) present a vivid, peculiar and most Judaizing model of the European Sabbatarianism. This research reveals the typological similarity of the Szombatosok, most of them ethnic Szeklers, with the Russian Subbotniks. The genesis of the Hungar ian sectarians is directly correlated to the European Reformation; Russian Judaizers are included in the context of the broad movement of ‘Protestantizing’. Those movements arose within the radical segment of the religious scene, and their development followed the path of gradual dechristianizing and reception of Judaism. Both in Transylvania and in Russia Sabbath keeping ideas were spreading mainly among peasantry. Religious views and practices of the Judaizers were initially being developed on the foundation of the Old Testament texts, while preserving Christian elements. The sectarians were persecuted by the authorities, invented comparable survival strategies, had similar identities and were powerfully impacted by the rabbinic tradition, which resulted in the conversion of the part of the dissidents to Judaism and their repatriation to Israel in the 20th century. At the same time, the Transylvanian model of Sabbatarianism has specific features. Unlike the autochthonous, ‘spontaneous’ popular movement of Russian Subbotniks, it was a kind of construct created and partly managed by representatives of the intellectual and social elite (both local and foreign), who preached their ideas to commoners. The transformation of Hungarian phenomenon towards Judaism took place not only due to contacts between religious communities and Jews, as in Russian sectarianism, but also to the leaders of the movement. The uniqueness of Szombatosok could be ascribed to the peculiarities of the genesis of the movement, the role of charismatic, highly educated personalities in its history, as well as the sociocultural and political context in which it developed.