Opening batter Sophie Molineux scored 59 off 41 balls as the hosts chased down South Africa’s 149-7 with four balls to spare.
Masabata Klaas was the visitors’ most successful bowler, taking 3-16.
Earlier, Nadine de Klerk scored 48* off 24 deliveries to help South Africa recover from 19-3 within four overs.
Courtney Sippel (2-20) and Chloe Ainsworth (2-31) were the pick of the bowlers for the home side.
Proteas Women’s tour of Australia:
27 January: 1st T20I, Manuka Oval, Canberra
28 January: 2nd T20I, Manuka Oval, Canberra
30 January: 3rd T20I, Bellerive Oval, Hobart
3 February: 1st ODI, Adelaide Oval, Adelaide
7 February: 2nd ODI, North Sydney Oval, Sydney
10 February: 3rd ODI, North Sydney Oval, Sydney
15-18 February: Only Test, WACA Ground, Perth
Photo: Mark Evans/Getty Images
