Argentina’s winning goal at the Maracana Stadium in Rio de Janeiro came in the 22nd minute after Rodrigo De Paul made a long pass to Angel Di Maria.
It was only the third goal Brazil conceded in the tournament.
Brazil piled on the pressure in an exciting second half but even with five strikers on the field, they could not get an equaliser against the Argentinian defence protected by the outstanding Rodrigo De Paul.
Argentina’s win was a particular triumph for Barcelona striker Lionel Messi, who picked up his first ever title in a blue and white shirt after more than 10 years of club and individual honours.
When the match ended, a tearful Messi was thrown into the air by some of his joyous teammates.
Messi finished the tournament’s joint top goalscorer with four goals and was elected joint best player with Neymar. But he was quiet throughout and uncharacteristically missed a golden opportunity to wrap the game up with two minutes remaining.
When the final whistle went, Argentina TV declared “Argentina Champions, Lionel Messi Champion!”
The victory was Argentina’s 15th Copa America triumph and means they draw level with Uruguay as the all-time leading winners.
Their win extended their sequence of undefeated matches to 20 under Lionel Scaloni and handed Brazil their first competitive defeat since they lost to Belgium in the quarter-finals of the 2018 World Cup.