The All Blacks Sevens, who were rattled in the first half by South Africa's showing, clawed back into the game in the second period.
First-half tries from Rosko Specman, former World Rugby Sevens Player of the Year Seabelo Senatla and HSBC Player of the Final Kwagga Smith put the Blitzboks 19-0 up against New Zealand, who were chasing their first tournament win since Vancouver in 2016.
The conversion sailed over to put New Zealand 7-5 up, while England lost Mitchell with an injury. A try in the last few seconds from Tim Agaba, however, sealed the 24-12 victory for the Blitzboks.More news: Mark Zuckerberg's sister sexually harassed on flight, Alaska Airlines launches investigation
"We kind of let them back into the game and a silly yellow card and one or two silly mistakes towards the end nearly cost us", Snyman said after the final.
It was the flawless start to the 2017/18 season after the success of the a year ago and the tonic the team needed ahead of this weekend's second tournament in Cape Town.
"It was a long pre-season and a lot of guys went on to play some XVs so it's a new team with some unfamiliar faces".
Smith was named player of the final for his hard-working efforts but he was quick to pass the praise on to his teammates.More news: NC Police: Missing three-year-old girl is believed to be dead
"We aren't focused on the result‚ we are focused on the processes and our aim is to leave the pitch happy knowing we did all we can‚ even if the result doesn't go our way".
Australia have been beaten after the final siren for the second straight match, falling to England in their Cup quarter final.
On the men's side, Canada split its opening games, with a 29-15 loss to Kenya followed by a 22-17 win over Uganda.More news: Pakistan happy to support SCO efforts for peaceful Afghanistan: PM Abbasi