South Africa's Siya Kolisi reacts after scoring a try against Argentina. Photo: Reuters
The victory, the Springboks' first away after four home wins this season, lifted South Africa level with title holders New Zealand on nine points apiece after two rounds. Australia have one point and Argentine none.
Flanker Siya Kolisi ran in two tries with flyhalf Elton Jantjies and replacement forward Jean-Luc du Preez scoring the others while the Springboks were also awarded a penalty try. Jantjies kicked 14 points for a personal tally of 19.
Wingers Ramiro Moyano and Matias Moroni scored tries for the Pumas, who lost Lavanini and Juan Manuel Leguizamon to the sin bin and had Lavanini sent off for a deliberate knockdown, his second yellow card offence, 23 minutes from the end.