Brazil took the lead when a cross from the right by striker Robinho, who seemed to be in an offside position when he received the ball from Kaka, was turned into his own net from close range by Keith Andrews one minute before halftime.
Substitute Daniel Alves should have doubled the lead after the break when he rounded Ireland keeper Shay Given and shot wide of the empty net.
"Robinho is someone who has always had big emotion for the national team and he was decisive today," Brazil coach Dunga told reporters.
"Sometimes people ... talk bad about him. Everybody can go through a good or a bad moment but ... certain players are very important to us and the whole team has to be behind those players."
"For 45 minutes we saw a very beautiful game," said Ireland coach Giovanni Trapattoni. "I think we played at the same level as Brazil.
"I thought in this moment we could also hope ... for a good result (but) the first goal was offside by one metre," added the Italian.
