The article deals with W.G. Schileico’s works on the history of the Mesopotamian religion (1912-1930). The contribution of the scholar to the study of incantations and divinations, calendar festivals and religious elements in epic texts is considered. The sources of publications have been revealed, as well as new archival materials have been included into scholarship. The ideas and hypotheses of the scholar are considered from the standpoint of modern Assyriology and the history of the Oriental religions. The study showed that W.G. Schileico, firstly, established a link between the apodosis of astrological texts and the epic Enuma elish. Secondly, he studied several periods of the cult of the god of fertility Dumuzi-Tammuz, drawing attention to the connection of these periods with the rite of the release of birds and the concept of redemption. Thirdly, he discovered the hierarchy of the moon and the sun in the ancient Middle East. Fourthly, he interpreted the image of Gilgamesh as a passion-bearer and pilgrim, and thus opened a prototype of the pilgrimage literature of the Middle East, which arose long before Christianity. Fifthly, he correctly defined the appeal to the oracle in the Sumerian economic text and thereby established the oldest cuneiform text with a mention of divination. Two methods of work of V.K. Schileico in different years of his scientific creativity are distinguished. The articles of 1912-1917 are written from positivistic point of view, there are visible severity of the grammatical analysis and philological skill in relation to work with the monuments. However, they are deprived of any theoretical generalizations. The second method of Schileico based on comparison of two or more texts developed in 1922. Texts were compared by criterion of external similarity of situations when ignoring internal conditions of their creation and inner logic.