Wingers Juan Imhoff and Emiliano Boffelli, center Jeronimo de la Fuente, flanker Juan Martin Gonzalez and replacement first-five Tomas Albornoz also crossed for the Pumas, who took advantage of Australian errors in ruthless fashion.
The Wallabies scored tries through captain James Slipper and center Len Ikitau, but bar a brief spell in the opening half never really threatened the hosts as the absence of leading players due to injury and personal reasons took its toll.
Only five of Australia’s starting XV had more than 30 caps and they never got to grips with Argentina’s intensity having beaten The Pumas 41-26 last weekend in Mendoza.
The home side kept applying pressure with ball in hand and attacking kicks, and while the bounce of the ball favored them, Australia were also their own worst enemies in not dealing with the threat.
“We really wanted to back (last week’s win) up but we fell short of standards today,” Slipper said.
“I thought the Argentinians were pretty good, they got the momentum behind them in the crowd and they’re a tough team to play catch up footy against.
“It’s been a really tough tour for us. We’ve got the South Africans twice at home now, we’re looking forward to that, getting back home in front of our fans.”
Argentina scored in the opening minute as Imhoff chased his own kick and when the ball was fumbled by Australia fullback Tom Wright, was able to race clear.
One try quickly became two as the home side powered over the line from close range, Gallo providing the finish touch.
The fast start continued as Australia finally got possession and after a barn-storming run from number eight Rob Valetini, Slipper crossed to score.