Pakistan won the toss and sent South Africa in to bat in the first one-day international at SuperSport Park in Centurion on Friday.
Pakistan captain Babar Azam said the presence of some moisture in the pitch influenced his decision to bowl first. Pakistan gave a first cap to batsman Danish Aziz.
Temba Bavuma, captaining South Africa for the first time, said South Africa would seek to post a total of about 280.
"There might be something in the wicket for the bowlers but on this ground we can score quite a lot at the end if there are wickets in hand."
Both teams opted for pace-based bowling attacks, with three specialist fast bowlers, one spinner and a seam-bowling all-rounder.
The three-match series is part of the International Cricket Council's World Cup Super League.
South Africa: Temba Bavuma (capt), Quinton de Kock (wkt), Aiden Markram, Rassie van der Dussen, Heinrich Klaasen, David Miller, Andile Phehlukwayo, Kagiso Rabada, Anrich Nortje, Lungi Ngidi, Tabraiz Shamsi
Pakistan: Babar Azam (capt), Imam-ul-Haq, Fakhar Zaman, Mohammad Rizwan (wkt), Danish Aziz, Asif Ali, Shadab Khan, Faheem Ashraf, Shaheen Shah Afridi, Mohammad Hasnain, Haris Rauf
Umpires: Marais Erasmus, Adrian Holdstock (both RSA)
TV umpire: Allahudien Paleker (RSA)
Match referee: Andy Pycroft (ZIM)