Rusty Bernstein was born to a middle-class family of Jewish émigrés. He was orphaned at the age of eight and he and his three siblings were raised by relatives. He finished his education at Hilton College, where he excelled academically although he hated the ethos of the school. After studying architecture at the University of the Witwatersrand, Rusty worked as an architect in Johannesburg.

Rusty joined the South African Communist Party and the Labour League of Youth, where he met Hilda, an immigrant from Britain. They were married in 1941. During the Second World War, Rusty served as a gunner in the South African army in North Africa and Italy, returning to South Africa in 1946.

Rusty was a private and reticent person, and a sensitive and articulate writer who wrote extensively for a number of journals. After the banning of the Communist Party in 1950, Rusty was active in forming the underground party and the Congress of Democrats, an organisation for whites that cooperated with the African National Congress, which at that time was restricted to black membership only. Rusty played a crucial role in drafting the 1954 Freedom Charter, writing the document's opening slogan, ‘Let us speak of freedom’, and giving its demands a sense of purpose with phrases like ‘the people shall govern’, and ‘all shall be equal before the law’.

In 1956, Rusty was arrested with 150 others and charged with treason, but acquitted after a trial lasting four years. In 1960 following the Sharpeville massacre both Rusty and Hilda were arrested and held for months without trial and were eventually released under banning orders.

Rusty was arrested again in 1963 at Liliesleaf Farm with leaders of the high command of Umkhonto we Sizwe, the military wing of the ANC. In what became known as the Rivonia Treason Trial, Nelson Mandela and seven of the other accused were sentenced to life imprisonment. Rusty was acquitted but immediately re-arrested. While out on bail, he and Hilda escaped into exile.

In London, Rusty practiced as an architect and continued to work for the ANC. He returned to South Africa in 1994 to run the ANC's press office during the first democratic election. Rusty was awarded the Order of Luthuli (Gold) posthumously for his political activism.