South Africa scored six tries in a 40-21 triumph over New Zealand Sunday in the final of the USA Sevens, fifth stop in the IRB Rugby Sevens World Series.
Branco du Preez scored two tries for South Africa, who had reached the final with a 12-7 semi-final win over defending US champions Samoa.
Paul Treu's South Africa dominated from the start, taking a 28-0 lead at half-time.
New Zealand rallied in the second half with three tries but had left themselves too much to do.
South Africa's victory made them the fifth side to win a Series title this season.
With the Hong Kong Sevens next up, March 22-24, New Zealand still lead the standings with 96 points ahead of South Africa on 73, Samoa on 71 and Fiji on 66.
"We haven't had this feeling for a while now, it's a while since we last won a Cup, so this is well deserved," Treu said.
"We put all the hard work in back in Stellenbosch, and every win gives you more confidence and hopefully we can build on this to use as a platform for the rest of the season."
New Zealand reached the final with a 19-14 victory over 2011 finalists Fiji, going through on David Raikuna's try in the corner.
Samoa claimed third place with a dramatic 36-31 victory over Fiji, surrendering an early lead only to win in sudden death with Robert Lilomaiava scoring the winning try.
Canada won the Plate with a 22-5 win over Scotland. Tries from Nanyak Dala, Conor Trainor and a 20th career try for John Moonlight lifted Canada, who had edged the United States 24-19 in the Plate semi-finals.
"It feels amazing, we have the home crowd support, the guys are playing well," said Canada captain Nanyak Dala.
France won the Bowl with a 17-12 win over Argentina, with tries from Terry Brouhroua, Renaud Delmas and Vincent Deniau.