However the South Americans lost first-choice right-back Danilo for the tournament after he hurt his right ankle early on and immediately called up Barcelona full-back Dani Alves, who was left out of coach Dunga’s original squad, to replace the Porto defender.
Brazil opened the scoring after 33 minutes in the southern city of Porto Alegre with a fine flowing move started by Filipe Luis in his own half.
The Chelsea left-back stormed forward, exchanged a one-two with Liverpool’s Philippe Coutinho and laid the ball off to Hoffenheim midfielder Firmino to slot home between the legs of the advancing goalkeeper.
It was one of the rare moments of quality in what was an uneventful match played in almost constant rainfall.
Striker Neymar, who was last to join the squad after playing in Barcelona’s Champions League win over Juventus, started on the bench and had a goal disallowed because of offside early in the second half before forcing a save from inside the arean in the 65th minute.
Former Manchester City forward Robinho, now of Santos, was also given a run in an uneventful second period.
“I think it was worth it,” Robinho said. “We are almost ready, we are growing each game, we have the same base and the trend is for that to continue.”
The result takes Brazil’s winning streak to 10 games since Dunga took over as coach after the 7-1 hammering by Germany in the World Cup semi-final last year.
Dunga’s men play Peru in their Group C opener in Temuco on Sunday before meeting Colombia and Venezuela.
The tournament begins on Thursday when hosts Chile play Ecuador.