Chanting "F*** off, France" and dressed in their trademark red T-shirts and caps, the Economic Freedom Fighters carried placards reading "West Africa is not a colony of the French" and "France must pay reparations for its colonial crimes".
"You killed a lot of people in Africa. Why are you so scared today?" the party's firebrand opposition leader Julius Malema shouted into a microphone, saying he was speaking to "French white supremacists".
Armed police guarded the embassy. French ambassador Aurelien Lechevallier emerged briefly to receive their demands.
"We are friends to African nations," he said.
The protesters arrived in buses hired by the party, according to AFP correspondents.
Malema, a master of political theatre, broke away from the ruling African National Congress nine years ago.
He has attracted millions of supporters, especially among workers and the unemployed. He routinely denounces European and American imperialism, and has supported Russia following the invasion of Ukraine.