The Springbok Women scored five tries to beat the UK Armed Forces 31-12 in Richmond on Friday.
Aseza Hele and Alana-Lee Horne scored two each, while the hosts could only manage two tries and a conversion.
The UK Armed Forces struck first with a converted try, but the Springbok Women found their rhythm early in the second quarter and hit back with two quick tries, by Horne and Hele, for a 12-7 lead.
The South Africans struck again late in the first half when Horne crossed to complete her brace for a 10-point lead going into the break.
The second half was closely fought as both sides defended well, but the hosts managed to break through and touch down with nine minutes left on the clock to reduce the deficit to 17-12.
But their hopes of a comeback were dashed as the Bok Women pulled away to secure the win.
Nosiphiwo Goda and Hele crossed the chalk, while the conversions were added by flyhalf Kirsten Conrad to wrap up the result.
South Africa will now play Tests against Wales in Cardiff, Spain in Villajoyosa, and Italy in Prato on 10, 17 and 25 November.