He created pieces for the Central Museum of Ethnology, the North River Terminal, several metro and railway stations and the Grand Kremlin Palace.

[1] His father, Semyon Grigorievich Efimov, was a government official and the illegitimate son of a Ukrainian peasant woman.

[3] Efimov grew up in an aristocratic milieu in the Tambov province on an estate known as "Otradnoe", to which later he would take his young bride.

[1] Between 1898 and 1901, he studied natural science at Moscow University, simultaneously taking painting courses under Valentin Serov and sculpture classes with Anna Golubkina at the art school founded by Elizaveta Nikolaevna Zvantseva.

[1][5] Between 1905 and 1908 he worked in Abramtsevo Colony in the ceramic workshop of Savva Mamontov creating toys, while continuing his studies at the Moscow School of Painting, Sculpture and Architecture (Russian: Московское училище живописи, ваяния и зодчества (МУЖВЗ)) with Serov, and studying sculpture with Sergei Volnukhin.

[1] In April 1906, he married fellow student and Serov's cousin, Nina Yakovlevna Simonovicha[6] and in 1909 the couple took a break from their studies at the Moscow School and went to Paris.

[7] Between 1909 and 1911, Efimov worked in the studio of Antoine Bourdelle[5] and beginning in 1910 studied sculpture with Filippo Colarossi and mastered the art of etching under the direction of Elizaveta Kruglikova.

He graduated with the title of sculptor in 1913 with his presentation pieces, Bison and Passion[1] and almost immediately went into service in World War I.

[5] Between 1935 and 1937, he sculpted a fountain, "Dolphins" for the North River Terminal[1] and between 1936 and 1937 created the sculpture "Old and New Moscow" for Gorky Central Park of Culture and Leisure.