Batting first at the Cardiff Stadium yesterday (24) South Africa scored 338 runs in 50 overs having lost seven wickets.
Hashim Amla (65), Captain du Plessis top scored with 88 while Vandersay chipped in with 40.
Suranga Lakmal and Nuwan Pradeep took two wickets each for Sri Lanka.
Chasing a massive score of 339, Sri Lanka only managed to score 251 runs havinf lost all their batsmen in 42.3 overs.
Captain Dimuth Karunaratne scored 87 and Angelo Mathews 64 contributed to boost the Sri Lankan innings while Andile Phehlukwayo took four wickets for South Africa.