Cape Town - Tladi Bokako and Nandre Burger shared six wickets as South Africa Emerging held off a late fightback to secure a 28-run win over Sri Lanka Emerging and go 1-0 up in their two-match four-day series late on day four in Potchefstroom on Sunday.
The pair helped the hosts bowl out the tourists for 302, chasing a victory target of 331 at Senwes Park.
Burger claimed three for 38 in 16 overs and Bokako nabbed three for 70 in 21.1 overs - the away side dismissed in 94.1 overs.
It means the Sri Lankans will now need to win the second match starting later this week in order to earn a share of the series, although they were relatively easy winners in a Triangular One-Day competition that ended a week ago when they beat University Sports South Africa (USSA) in the final.
Their slow start to this game ultimately proved costly after the hosts amassed 382 in the first innings thanks to Matthew Breetzke, with the reply being an under-par 241.
They then restricted Shukri Conrad's side to just 189 in the second innings and appeared to be the favourites heading into the final day after reaching stumps on day three at 145 for one.
But the South Africans managed some early blows, particularly the first one that accounted for the set Minod Bhanuka 14 runs into the morning when Bokako had him caught behind by Sinethemba Qeshile for 89 (134 balls, 12 fours).
Captain Charith Asalanka (9) and Ashen Bandara (1) then followed as Bokako again struck, along with Marco Jansen (2/58), who got rid of the former, suddenly leaving the Asians on 173 for four.
Dayyaan Galiem (1/37) tilted things more in the hosts' favour when he had the other key man, Pathum Nissanka (47), also edging to Qeshile.
And, when Burger trapped Kamindu Mendis (17) and Chamika Karunaratne (10) leg before wicket, the end looked near - Sri Lanka slipping to 214 for seven.
A 58-run eighth-wicket stand between Mohamed Shiraz (49) and Nishan Peiris (25) had helped their side roar back, but when the stand was eventually broken, the fast bowlers wrapped up the tail to give the South Africans a morale-boosting win.
The second and final match of the tour begins in Pretoria from Thursday.