Batting first at the Barabati Stadium, Sri Lanka put up a decent score of 243 for seven in stipulated 50 overs with useful contributions from the middle-order.
In reply, South Africa were bundled out for a paltry 156 in only 40.1 overs with off-spinner Shashikala Siriwardene picking up four for 32.
Among the Lankan batswomen, Chamari Atapattu was the top-scorer with a patient 52 off 106 balls. She hit five boundaries. The other contributions came from Deepika Rasangika (43), Siriwardene (44) and Eshani Kaushalya (43).
While replying, barring Shandre Fritz, who scored 54, none of the other batters were able to get on with the chase as the Lankan bowlers had complete control.
Sripali Weerakkody (2/15) and Chamani Seneviratna (2/35) kept things tight as they polished off the top-order while Sriwardene then came on to run through the middle and lower-order.