A forester's son, Richard Dehmel was born in Wendisch-Hermsdorf (now a part of Münchehofe) in the Brandenburg Province of the Prussian Kingdom.

Expelled from a Berlin gymnasium after conflicting with his teachers, he finished his schooling in Danzig and studied the natural sciences, economics, literature, and philosophy at university, where he submitted a thesis in economics. Subsequently employed as a secretary at a fire insurance association, he remained in the same occupation until beginning to write full time after the publication of his second volume of poetry.

In 1889, he married Paula Oppenheimer, sister of Franz Oppenheimer. He became active as a writer, and was co-founder of the PAN magazine in 1894.

Dehmel divorced Paula in 1899 and traveled around Europe with Ida Auerbach (née Coblentz), whom he married in 1901, and settled in Hamburg in the same year.

Dehmel's poetic volume Weib und Welt (Woman and World) triggered a scandal in the late 1890s: denounced by the deeply conservative poet Börries von Münchhausen, Dehmel was tried for obscenity and blasphemy. Despite his own acquittal for Weib und Welt on technical grounds, the court condemned the work as obscene and blasphemous and ordered that it be burned. Dehmel would again be prosecuted for obscenity and blasphemy, but again acquitted as earlier.

Despite his earlier record of fighting against the conservatives, Dehmel joined the resounding chorus of the patriotic and pro-war German intellectuals who appealed to the masses to support the Reich upon the outbreak of the First World War in 1914. Fifty-one at the time, Dehmel volunteered in 1914 and served until 1916, when he was wounded. He called on the Germans to keep fighting right until 1918. Dehmel died in 1920 of the injury he suffered during the war.

Dehmel is considered one of the foremost German poets of the pre-World War I era. His poems were set to music by composers like Richard Strauss, Max Reger, Alexander von Zemlinsky, Arnold Schoenberg, Anton Webern, Ignatz Waghalter and Kurt Weill, or inspired them to write music. Dehmel's main theme was "love and sex (Eros)", which he conventionalized as a power to break free from middle class bounds.