New Zealand won the toss and elected to bat first, but were bowled out for 91 on a difficult wicket.
South Africa reached their target with 20 balls to spare, but it was hard graft for a side featuring four debutants – Mokoena, batters Connor Esterhuizen, Dian Forrester and Jordan Hermann.
The wicket took turn and was helpful to the seam bowlers, with plenty of bounce as well in what was a difficult outing for the batters.
Mokoena returned excellent figures in a strong all-round bowling effort from the South Africans, with seamers Gerald Coetzee (2-14 in 3 overs), Ottneil Baartman (2-22 in 3) and captain and spinner Keshav Maharaj (2-25 in 4) also contributing.
Jimmy Neesham (26 from 21 balls) was the only New Zealander to provide anything remotely constituting a useful score in their innings.
South Africa’s innings was anchored by opener Esterhuizen, who scored a measured unbeaten 45 from 48 deliveries.
There were only 11 fours and five sixes scored in the entire match.
The series is also being played in conjunction with the women’s national teams of both sides in double-headers and in that contest New Zealand dominated with an 80-run victory.