The article is devoted to the analysis of the theme of the history of Decembrism in the works of G. V. Vernadsky. The study of freemasonry in the Catherine's epoch led Vernadsky to the history of secret lodges of the beginning of the 19th century, and they, in turn, being the initial page of the history of Decembrism, attracted his attention to the study of secret societies. Unfortunately, the pivotal years of the civil war and the ordeals of relocation did not permit G. V. Vernadsky to complete the work on this topic by monographic research. But according to the surviving materials, we see that his observations became an organic continuation of the pre-revolutionary historiographic tradition within which he was formed. He proposed his own outline of the evolution of the political thinking of the figures of the secret society and analyzed the features of the ideological struggle within the framework of the Decembrist organizations. He appealed to the important problem of the influence of governmental constitutionalism on the formation of the program documents of the Decembrists. After emigration, the historian's scientific interests shift toward ancient Russian history. Nevertheless, in works of different years he addresses to the Decembrist subjects. In the postwar period, he makes a public lecture, the text of which is published as an annex to the proposed article. This text can be dated to the year 1947. The historian aspires to assess the place of the Decembrists in Russian history. It shows how significant and crucial the epoch for the development of the country was the first quarter of the 19th century. And in conclusion he offers his listener to imagine: how would history have gone if the Decembrists had won?.