Sergey Lomonosov graduated from the Tsarskoye Selo Lyceum with a silver medal in 1817 and then began his career at the Ministry of Foreign Affairs.
Upon his return to St Petersburg in 1821, Sergey Lomonosov was sent to Spain to assist Count Mark Bulgari (a Russian charge d'affairs).
In 1831, Sergey Lomonosov was appointed chargé d'affaires to Copenhagen and then as first secretary to London.
During his stay in South America, he travelled along the Brazilian coast from Rio de Janeiro to the estuary of the Amazon River and probably became the first Russian ever to introduce this country to Russia.
In 1853, he was appointed envoy extraordinary and minister plenipontetiary at the Dutch Royal Court, keeping this post until his death in 1857.