Costa Gazi was an anti-apartheid activist in the underground South African Communist Party (SACP) and later the Pan Africanist Congress of Azania (PAC), both of which were illegal organisations. Post-apartheid, he has worked as head of public health at Cecilia Makewane Hospital in Mdantsane, East London, South Africa, where he criticized the policies of the ruling African National Congress (ANC), notably the AIDS denialism of then-President Thabo Mbeki.