The major developments in the life of Vasiliy P. Vasilyev (Wassiljew) (1818-1900), a Russian academician-sinologist, as well as his works are quite familiar. However, further efforts need to be taken to research new archival documents concerning obscure pages of his life. In keeping with this, the authors of the article describe, for the first time in Russian historiography, Vasilyev's stint in Beijing from 1840 to 1850. He arrived there as a scholar of the Russian Ecclesiastical Mission. This part of Vasilyev's life and scholarly work was covered due to some newly found documents in the National Archives of Tatarstan. After he defended his dissertation on the Philosophy of Mongolian Buddhism in 1840, Vasilyev, Master of Philosophy, was invited to work at an opening Chair of the Tibetan language, Kazan University. Aiming to implement its intention, the Kazan University sent him to Beijing, with the support from the Ministry of Public Education and Ministry of Foreign Affairs. Apart from studying Tibetan and Sanskrit, he was charged with the difficult task to purchase books for the Academy of Sciences and the Kazan University, including Chinese and Manchurian works in history and geography. His work in Beijing was made harder due to a number of circumstances, particularly, the opposition between the clerical and secular members of the Russian Ecclesiastical Mission in Beijing. The conflict involving Vasilyev lasted throughout 1842-1844, which made him insist on returning to Russia. Vasilyev's detailed reports and other documents which possess certain assessments of his activities allow to judge how differently the top officials from the Ministry of Public Education and his own senior colleagues, academics from the Kazan University, appraised the scholarly outcome of his mission. The academic and research plans set before Vasilyev were fulfilled and overfulfilled by the young researcher. Among other things, he gathered a large collection of resources on the history of Buddhism in Central Asia and Far East