At least 18,000 people and 5,000 vehicles gathered at Kanonkop, a farm in Klapmuts near Stellenbosch to protest against farm murders.
The City of Cape Town's Richard Bosman said the group "Genoeg is Genoeg" (Enough is Enough) was given a permit to stage demonstrations on Sunday, but the number of people exceeded what the City planned for.
The farmers have called on all South Africans to wear black in commemoration of those killed on farms.
The South African Police Service (SAPS) accompanied the protesters.