He was one of the earliest scientific explorers of the Pacific region, making significant collections of flora and fauna in Alaska, California, and Hawaii.

[1] He studied medicine and zoology at the University of Dorpat and served as an assistant to Carl Friedrich von Ledebour, a professor of botany.

On the recommendation of Ledebour, Eschscholtz served as surgeon and naturalist on the Russian expeditionary ship Rurik under the command of Otto von Kotzebue.

[4] The expedition left Kronstadt, Russia, on 30 June 1815, stopping at the Canary Islands in September and then crossing the Atlantic to Santa Catarina, Brazil.

When Kotzebue became ill in 1817, they cut short a planned return to the Arctic and headed home, stopping again in Hawaii and then in the Philippines before ending their voyage at St. Petersburg in August 1818.

[1] In 1823, Kotzebue was commissioned to return to the North Pacific to resupply Kamchatka and then proceed to Alaska to protect the Russian American Company from smugglers.

Eschscholtz published illustrated descriptions of the new fauna he encountered in Zoologischer Atlas, 1829-1833; and provided further information in System der Akalephen, 1829.