Lionel Messi returned from international suspension to score the winner in Argentina's 1-0 victory over Brazil in Saudi Arabia on Friday.
The Barcelona striker, who missed four games after calling the South American Football Confederation "corrupt," scored after 14 minutes to give Argentina a deserved victory in the so-called Superclasico.
The result extended Brazil's winless run to five games since they lifted the Copa America in July, their worst such run since 2013.
Brazil beat Argentina 2-0 the last time these teams met in the Copa America semi-finals and they should have taken a ninth minute lead but Gabriel Jesus fired a penalty kick wide after he had been brought down in the box.
Argentina were also awarded a penalty five minutes later and although Brazilian keeper Alisson saved Messi's initial effort, the Barcelona striker followed up to put Argentina 1-0 ahead.
Messi missed two chances to double Argentina's lead before half-time, with defender Eder Militao and Alisson blocking the opportunities.
Brazil, who were without Paris St Germain striker Neymar, had two-thirds of the possession but rarely threatened the Argentine goal in a game that featured 41 fouls and six yellow cards.
Argentina have now won three of the five games they have played since their semi-final exit at the Copa America.