Cape Town - Portugal were no match for the Blitzbokke in their opening Pool D match at the London 7s, losing 19-0 at Twickenham on Saturday.
The South Africans, aiming to snatch the world Sevens title from Fiji, started off their London campaign with a comfortable win.
The Blitzbokke led 7-0 at the break through a Stephan Dippenaar try.
Dippenaar waltzed over in the corner for his side's second try before Rosko Specman scored the final try for the Blitzbokke in the dying seconds of the match.
Branco du Preez contributed with two conversions.
South Africa v Portugal - 13:06
South Africa v USA - 16:34