Born at Rostov-on-Don, now in Russia, and educated at the Leningrad Industrial Institute of Science, Flerov started his career at the Leningrad Institute of Physics and Technology in 1938. He later became chief of the laboratory of multicharged ions at the Kurchatov Institute of Atomic Energy, Moscow.

Throughout his life, Flerov was involved in the search for new elements and isotopes through synthesis and discovery. In many ways his work paralleled that of Glenn Theodore Seaborg and his research team in America.

Flerov and his coworkers synthesized and analyzed isotopes of elements 102, 103, 104, 105, 106, and 107 (members of the actinide group and transactinides) by bombarding nuclei of heavy elements with heavy ions in a cyclotron. In particular, they have a claim to the first discovery or identification of transactinide elements 104 (1964) and 107 (1968). The correct attribution of these discoveries is still in dispute. Besides his work on the transuranic elements, Flerov was also involved in the search, both by synthesis and discovery in nature (possibly in cosmic rays), of the postulated superheavy elements. Many theorists believe that although elements beyond the actinides in the periodic table would be highly unstable, there may be ‘islands of stability’ at higher atomic numbers, if they can only be reached.

In 1960 Flerov became director of the nuclear radiation laboratories of the Joint Institute for Nuclear Research, Dubna, near Moscow.