The Blitzboks beat England 14-10 at the Wellington Sevens to finish top of Pool B.
South Africa trailed 5-0 at the break, but took the lead when Mark Richards scored a try early in the second half. Branco du Preez then beat three defenders to give his side a nine-point cushion.
England scored their second try in the final minute of the match, but the Blitzboks secured the kick-off, won a penalty and booted the ball into touch.
Earlier in the day, Cornal Hendricks scored a brace in South Africa’s 43-0 hammering of the Cook Islands in Wellington.
Paul Treu’s charges shot to a 19-0 half-time lead thanks to tries by Hendricks, Steven Hunt and Boom Prinsloo. Frankie Horne scored soon after the restart while Hendricks added his second two minutes in. Cecil Afrika and Paul Delport added further tries to complete the rout.
The Blitzboks also recorded a 21-0 win over the United States of America. Afrika scored a brace while Hunt also got his name on the scoresheet.
South Africa will play Fiji in the Cup quarter-finals on Saturday.
For all the results, click here.