Beginning his training at the Imperial Academy of Arts with Anton Losenko in 1764, he went to Rome in 1774 and then to Paris in 1779.

Although his early works harked back to the Baroque sensibility, Kozlovsky eventually succeeded in adapting his manner to Neoclassical monumentality.

He was appointed a professor at the Academy of Arts in 1794 and instructed young sculptors in St Petersburg until his death.

Among his classicizing works was the awesome gilt bronze statue of Samson Rending the Lion's Jaws (1800–1802), a central piece of the Grand Cascade at Peterhof Palace, symbolizing Russia's victory over Sweden in the Great Northern War.

It was unveiled in the Field of Mars (Saint Petersburg) a year before the sculptor's death.