Julio Baptista scored his third goal in three games at the tournament when he gave Brazil the lead after just four minutes.
The striker, unwanted by Arsenal, picked up a long ball from Elano, who had replaced suspended skipper Gilberto Silva, and controlled it neatly.
He turned to the right of Argentina skipper Roberto Ayala and fired a fierce right-foot drive into the top corner of Roberto Abbondanzieri’s goal.
Five minutes later, Argentina were unfortunate not to be back on level terms.
A cushioned header from Juan Sebastian Veron found Juan Roman Riquelme in space but the playmaker’s left-foot shot came off the post with goalkeeper Doni well beaten.
|Argentina lost their chance to win a record
15th Copa America title [Reuters]
At the other end, Abbondanzieri saved from Maicon to keep the deficit down while opposite number Doni was also alert to danger when he thwarted another Riquelme effort 10 minutes from half-time.
Brazil, who were without superstars Ronaldinho and Kaka, went 2-0 ahead in the 40th minute when a right-wing cross from substitute Daniel Alves was turned into his own goal by Ayala whose 115th international appearance turned into a nightmare.
Argentina continued to struggle to make any impact at the start of the second half as the likes of Carlos Tevez and Lionel Messi were marked out of the game by well-organised opponents with central defenders Juan and Alex particularly solid.
Brazil earned the reward for their superiority with a memorable third goal after 69 minutes.
Vagner Love broke free down the left and slotted an inch-perfect pass between two defenders where Alves, who plays for Spanish side Svilla, was waiting.
The substitute made no mistake with a low drive into the corner past Abbondanzieri to score his first international goal.
Argentina’s miserable night was summed up when Tevez had an 80th-minute effort ruled out for offside.