Pyotr Derber was born in Odessa into a family of a clerk. He graduated from a vocational school, and later he studied at the Law Faculty of Tomsk University. A Socialist Revolutionary Party (SRP) member since 1902. He was arrested several times. In 1905, Derber was exiled to the Tobolsk governorate and subsequently lived in Siberia, where he was engaged in activities for the Party. A member of the cooperative movement. In 1916, in Omsk, he was the secretary of the working group in the Military-Industrial Committee.

After the February Revolution of 1917, he became the leader of Omsk Socialist-Revolutionaries (SRs). A member of the Omsk coalition committee, Chairman of Akmolinsk regional land committee. In May–June 1917, he was a delegate to the 1st All-Russian Congress of Peasant Deputies, where he acted as an opponent of Vladimir Lenin on the agrarian issue. The Chairman of three Western Siberia congresses of peasants’ deputies.

He accepted the October coup with hostility. Derber was an active figure in the Siberian oblast movement (social and political movement for the autonomy of Siberia). A participant of the First (October) and Second (December) Siberian regional congresses held in Tomsk. A deputy of the Constituent Assembly representing the Steppe constituency.

In December 1917, he was elected a member of the Provisional Siberian Regional Duma in Tomsk. After its dissolution, an illegal meeting of MPs elected him as Chairman and interim minister of agriculture in the Provisional Siberian Government.

In March 1918, as he had no opportunity to really administrate any territory, Derber left for Harbin. He conducted negotiations trying to talk Dmitry Khorvat, the manager of the Chinese Eastern Railway (CER) government to hire Admiral Aleksander Kolchak, and sought support from the United States. After the Czechoslovak Legion captured Vladivostok, Derber with a group of like-minded people moved there. Since June 29, 1918, he combined the positions of the Chairman of the Provisional Government of Autonomous Siberia, Minister of Agriculture, and the administrator of the Ministry of Foreign Affairs. He did not recognize the Provisional Siberian Government headed by Pyotr Vologodsky, established in late June 1918. He resigned as Chairman of the Government in July 1918 and left all ministerial posts in September.

After the Omsk coup of Aleksander Kolchak (November 1918), Derber served as an agent for the purchase of meat in Altai and conducted underground work. In August 1919, he was arrested in Tomsk and imprisoned in Semipalatinsk. He was released by insurgent soldiers. At the end of December 1919 – January 1920, he held the post of political commissar of the 4th Peasant Corps of the West Siberian Peasants’ and Workers’ Guerilla Army. He collaborated with the Soviet government, worked in Omsk and Novosibirsk.

1922 saw him arrested during the preparation for the trial of the Social Revolutionaries. His case (over the counter-revolution in Siberia) was subsumed under a specific legal provision. He was sentenced to 5 years in prison. After the release, Derber lived and worked in Moscow. In 1938, he was arrested, sentenced to capital punishment by the Military Collegium of the Supreme Court of the USSR over alleged involvement in a counter-revolutionary terrorist organization, and shot. He was rehabilitated in 1991.