Avksentiev was born into a noble family in Penza. He studied at the Faculty of Law of Moscow University. After he organized a students’ strike, Avksentiev was expelled without the right to reenter and exiled to Penza. He resumed his education abroad, studied at a number of German universities, and obtained his Ph.D. During his studies in Germany, he joined a circle of Russian students, which later included the leaders of the Socialist Revolutionary Party (SRs) Abram Gots, Vladimir Zenzinov, Ilya Fondaminsky.

After the start of the First Russian Revolution of 1905–1907, he joined the Socialist Revolutionary Party and was elected to its Central Committee. Avksentiev represented the SRs in the St. Petersburg Soviet of Workers’ Deputies. In December 1905, he was arrested along with other leaders of the Soviet. In 1906, he was convicted, stripped of nobility, and exiled to Obdorsk (currently Salekhard). In 1907, he fled from exile to Finland [which was then part of the Russian Empire], then abroad, where he became the leader of the SRs’ right wing. Upon the outbreak of World War I, he became an active advocate of oboronchestvo [defencism], and joined the editorial staff of Prizyv (originally, a newspaper, and later a magazine) (1915 – early 1917), together with Georgy Plekhanov and others.

After the February Revolution of 1917, he returned to Russia. In May, he took over as Chairman of the Executive Committee of the All-Russian Soviet of Peasant Deputies. He was a member of the Commission for Elections to the Constituent Assembly. From July 24 to September 2, 1917, he was the Minister of Interior of the Provisional Government. He authorized the arrest of Bolshevik leaders and the closure of several radical newspapers. Avksentiev was the founder and Chairman of the Provisional Council of the Russian Republic (Pre-Parliament).

His attitude to the October coup of 1917 was highly negative, and he established the Committee for the Salvation of Motherland and Revolution. He was elected an MP (deputy) of the Constituent Assembly. December 1917 saw him arrested and imprisoned in the Peter and Paul Fortress. After People’s Commissar for Justice Left SR Isaac Steinberg intervened, Avksentiev was released.

In March 1918, he became a founder of the Russian Revival Union. In May 1918, in the context of the armed uprising of the Czechoslovak Legion in the Volga region and Siberia, the Central Committee of the Socialist Revolutionary Party sent him to the east of the country to establish an anti-Soviet coalition government. In September 1918, he headed the State Conference in Ufa, which established the new Provisional All-Russian Government (Ufa Directorate). Avksentiev became its Chairman. On his initiative, this government was relocated to Omsk to promote the unification of all anti-Bolshevik forces.

During the Omsk military coup, on November 18, 1918, Avksentiev was arrested. He was exiled to China. Since the spring of 1919, he lived in Paris. He advocated armed struggle against the Soviet regime. In 1921, he became Chairman of the Meeting of Members of the Constituent Assembly.

In 1940, he moved to the United States, where he supported the anti-fascist struggle of the Soviet people. Avksentiev died in 1943 in New York.