Dunga has been named successor to Luiz Felipe Scolari as Brazil coach.
The 1994 World Cup-winning captain on Tuesday afternoon conducted a press conference after being appointed manager by Brazil's Football Confederation.
Scolari resigned after Brazil finished fourth in the recent World Cup they hosted, suffering a humiliating 7-1 semi-final rout by Germany in the process.
Dunga coached Brazil at the 2010 World Cup in South Africa but was sacked following a 2-1 defeat by Holland in the quarter-finals.
His record during the four years of his first reign read won 42, drew 12 and lost six. He has beaten former Corinthians manager Tite to the post.
The 50-year-old's first game in charge will be a rematch with defeated 2014 World Cup quarter-final opponents Colombia in Miami on 5 September.
Dunga launched his second spell at the helm with an attempt at dampening expectations of the national side by stressing that Brazil always have a target on their backs.
"I'm very happy for the opportunity the CBF (Brazil Football Confederation) have given me. We need to stop thinking we're the best and work harder," Dunga told reporters.
"Before the World Cup happens we sell to the public the idea we're going to win, but we don't know if we'll win.
"We need to be more modest. It's important to compromise because our opponents always want to beat us because we're Brazil.
"The Brazilian shirt is very respected, but everyone wants to beat us. We have to be prepared for that.
"We can't think that we'll pull on the Brazilian shirt and win the World Cup before it's even started.
"Nothing happens before the game starts. The most important thing is what happens during the 90 minutes on the pitch because that's when you win or lose."