President Jacob Zuma led an official ceremony to receive the bodies of Moses Kotane and John Beaver Marks, whose bodies were exhumed from Russia's prestigious Novodevichy cemetery in Moscow.
Kotane, ex-general secretary of the South African Communist Party and a former executive committee member of the African National Congress (ANC), was one of 156 defendants in the notorious 1956 treason trial.
The group, which included Mandela, was arrested in a raid and charged with treason by the apartheid regime. All the accused were found not guilty by the time the trial ended in 1961.
"Our very own icon Nelson Mandela is a product of these two," said Zuma. "They are the fathers of our revolution".
Born in 1905, Kotane fled the country into exile to Tanzania in 1963 where he helped coordinate the setting up of the ANC military wing Umkhonto we Sizwe.
In 1968, Kotane suffered a stroke and was flown to Moscow for treatment where he died in 1978.
Zuma secured the repatriation from his counterpart Vladimir Putin during a visit to Russia last year.
"A valiant, courageous and stubborn fighter has fallen at his post, on the battlefield," is how former ANC president Oliver Tambo described Kotane in a eulogy.
Fellow veteran activist Marks was banned from the country by the apartheid regime and sought asylum in Russia. He also died after suffering a stroke in Moscow in 1972.
They will be buried at state-assisted funerals later this month.
Last year the remains of prominent anti-apartheid journalist and writer, Nat Nakasa, were repatriated from the United States of America, nearly 50 years after he committed suicide while in exile.
