Cape Town - The Springbok Sevens side reached the last four of the Paris Sevens after beating Samoa in their Cup quarter-final clash on Sunday.
The Blitzboks won an intensely physical encounter 12-0.
Two first half tries from Cecil Afrika and Werner Kok were enough to see the South Africans past the South-sea Island team.
Samoa threw everything they had at the Blitzboks in the second period, but staunch defence kept them at bay.
South Africa will now face New Zealand the semi-finals at 14:40, while Scotland and England will contest the other semi-final at 14:18.
In pool stage action on Saturday, the Blitzboks reached the quarter-finals after winning two of their three matches.
The South Africans lost 19-12 to Scotland, before rebounding to beat Japan (35-5) and Canada (31-7).
Tries: Cecil Afrika, Werner Kok
Conversion: Branco du Preez