In a re-match of the FIBA Americas Championship final won by Argentina last year, they looked comfortable when Manu Ginobili's three-pointer gave them an 70-59 lead with seven minutes left to play.
But Brazil had other ideas. The outstanding Marcelinho Huertas added two points from the free-throw line to start a 9-0 charge that got it to 70-68 on Alex Garcia's lay-up.
Pablo Prigioni padded the lead for Argentina and Nene Hilario came up empty with a pull-up jumper before Andres Nocioni gave Argentina a 74-68 edge.
Prigioni missed a three and Carlos Delfino a short jumper for Argentina
Leandro Barbosa took advantage to slice the lead back to 74-71 with less than two minutes to go.
Prigioni missed another three, but Marcelinho came up empty when given the chance to tie with another three.
From there, Argentina closed it out from the free-throw line with Ginobili, Luis Scola, Delfino and Prigioni all perfect from the line to make it 82-71.
Leandro had back-to-back three-pointers late on to slice the margin, but time ran out on another rally.
Scola led Argentina with 17 points while Ginobili and Delfino had 16 each, Ginobili also grabbing eight rebounds.
Andres Nocioni scored 12 and Jonas Gutierrez 11 in a balanced offensive showing.
Brazil relied heavily on Marcelinho and Barbosa, who had 22 points each.