President Buhari had earlier presided over the weekly meeting of the Federal Executive Council (FEC) before embarking on the trip.
The visit comes against the background of recent xenophobic attacks, the evacuation of hundreds of Nigerians and the exchange of visits by special envoys of Presidents Buhari and Ramaphosa.
While in Pretoria, the Nigerian leader will hold bilateral meeting with his South African counterpart, President Cyril Ramaphosa, to discuss the welfare of Nigerians.
The two African leaders will also find common grounds for building harmonious relations among their respective citizens.
President Buhari will hold a town hall meeting with Nigerians living in the country to share in their experiences.
An earlier statement on the trip issued by Malan Garba Shehu, the President’s spokesperson, said the Nigerian leader would use the opportunity to reassure Nigerians in South Africa of the Nigerian government’s commitment to working for the protection of their lives and property and promoting peaceful co-existence.
The president is expected back in Abuja on Friday.