Argentina ended an 11-match losing streak in the Rugby Championship spanning three years when they upset South Africa 32-19 in Mendoza on Saturday.
Fly-half Nicolas Sanchez starred for the Pumas in the second-round match, scoring 17 first-half points as they built a 27-7 half-time lead at Estadio Malvinas Argentinas.
South Africa, who triumphed 34-21 when the teams clashed in Durban last weekend, dominated the second half but could only outscore Argentina by two tries to one.
New Argentina coach Mario Ledesma demanded more passion and better defending after the first-round loss and he got it before a vocal 27,460 crowd.
As much as the Pumas sparkled when attacking in the first half, they repeatedly held the dominant Springboks at bay during the second half.
New Zealand, who crushed Australia 40-12 in Auckland, top the standings with 10 points followed by South Africa with five, Argentina on four and Australia are pointless.
Sanchez opened the scoring on a clear day in western Argentina with a penalty as the South Americans sought revenge after conceding six tries in Durban last weekend.
But a visiting team who have been slow starters in Tests this season hit back with skipper Siya Kolisi racing over for a try which Handre Pollard converted.
It took five minutes for the highly charged Pumas to regain the lead with a brilliant line break leading to a try in the corner by Bautista Delguy.
The winger scored again in the same corner soon after as Argentina once again exposed poor blind-side defending by South Africa.
Sanchez converted both tries and then scored one himself after a scrum following the yellow-carding of Springbok lock Eben Etzebeth for a professional foul.
The 'little general' converted his try and Argentina had turned a four-point deficit into a 17-point advantage in a stadium at the foothills of the snow-capped Andes mountains.
Sanchez was not finished tormenting South Africa, though, as he slotted a drop goal on 37 minutes to complete the first-half scoring and leave the Pumas 20 points ahead at the break.
Argentina were full value for the big lead, showing a particularly dramatic improvement from last weekend when scrumming.
Perhaps it was a lack of faith in off-form Pollard, who fluffed a simple early penalty, but South Africa spurned several shots at goal, opting for kicks to touch that yielded nothing.
The second half saw a dramatic change of roles with South Africa attacking and Argentina defending.
But the Pumas stretched their lead to 25 points when Ramiro Moyano went over and Sanchez missed a shot at goal for the first time in the match when his conversion drifted left.
Lionel Mapoe, an early substitute for Makazole Mapimpi, scored two tries, but Pollard converted only one to leave South Africa trailing 32-19 with 15 minutes left.
They failed to score again with Argentina winning some crucial turnovers and Guido Petti stealing a couple of South African lineout throws.
Tries: Delguy 2, Sanchez, Moyano
Cons: Sanchez 3
South Africa 19
Tries: Mapoe 2, Kolisi
Cons: Pollard 2