The Blitzboks beat Spain 24-12 and will now face Ireland for fifth spot at London Sevens at Twickenham.
Branco du Preez opened the scoring against the Spanish with his 100th try for the Blitzboks soon after the start of the game to give the Blitzboks a 7-0 lead.
Jerry Davoibaravi hit back almost immediately for Spain as he raced away from the South African defence to score under the poles and tie the game up at 7-7.
Spain then took a 12-7 lead as Carlos Sainz-Trapanga was quickest to react to a kick through from his brother Tobias to score an unconverted try.
Mfundo Nohlovu levelled it up for the Blitzboks as he pounced on a loose ball, controlled the ball with his foot and collected and scored as the teams went into half-time at 12-12.
The Blitzboks were the fastest out of the block in the second half with Angelo Davids the scorer of a converted try and a 19-12 lead.
Skipper Siviwe Soyizwapi sealed the match with a try in the left-hand corner with no time left on the clock as the Blitzboks ran out 24-12 winners.
Earlier, in the quarter-finals, South Africa raced into a 17-0 lead, but an emphatic fightback by Australia saw them run out 21-17 winners.
