Morne Steyn was on target with all three conversions and two penalties to grab 12 points for the home side and the home tries came from full back Zane Kirchner and flanker Marcell Coetzee, in the first half, and Bryan Habana after the break.
Santiago Phelan, the Argentinean coach, will rue the three penalty misses in the first 20 minutes of the second half, but of greater concern to him will be that his side never looked like scoring a try.
The two sides meet again in Mendoza on Saturday in the Pumas' historic first home game in a global tournament.
