Bogumił Jasinowski (1883–1969), a Polish philosopher and specialist in Russian culture, was also interested in the issues of Gnosticism and Manichaeism. Although he had dealt with this subject for around forty years, however he did not devote any separate publication to it. For this reason, the author of this paper has to reconstruct Jasinowski’s views on mentioned issue on the basis of his texts on Russian and philosophical topics. The Polish philosopher regarded Gnosticism and Manichaeism as one of the most important phenomena in the history of religion, and particularly in the history of Christianity. Jasinowski, using the original method, juxtaposed Gnosticism with Neoplatonism and with Indian philosophical and religious systems; he also proposed his own characteristics of Gnosticism. For the Polish philosopher, the Gnostic and Manichaean worldview was the important factor in interpreting Russian spirituality and culture, and even such a phenomenon as the Bolshevik Revolution. This interpretation caused a polemic on the part of Marian Zdziechowski and Nikolay Lossky.