Fyodor Dan was born to a Jewish family in St. Petersburg, where his father owned a pharmacy.

He participated in the social democratic movement from 1894[2] Dan was a lifelong socialist activist and journalist.

He was a member of the St. Petersburg Union of Struggle for the Emancipation of the Working Class and was one of the organizers of the textile workers' strike.

On his return, he joined the Russian Social Democratic Labour Party in 1902 and went to London for their Second Congress in 1903.

[6] Dan was arrested on the order of the Soviet authorities in 1921 and after a year in prison was sent into exile on charges of being an "enemy of the people".

After the death of Julius Martov in 1923, until 1940, he headed the Foreign Delegation of the Menshevik faction of the RSDLP.