Antony, Pedro and Gabriel Martinelli had some of the best opportunities for Brazil, while Aboubakar had already come close for Cameroon.
Brazil finally conceded an attempt on target after not having done so in the first two matches.
Cameroon, which opened with a 1-0 loss to Switzerland, had endured a small crisis after its 3-3 draw with Serbia, with goalkeeper Andre Onana being sent home for disciplinary reasons after a dispute with coach Rigobert Song.
Cameroon didn't qualify for the last World Cup in Russia four years ago.
ALVES' RECORD
With his start Friday, the 39-year-old Dani Alves became the oldest Brazilian to play at a World Cup, ahead of 38-year-old central defender Thiago Silva, Brazil's captain in Qatar. Alves' last game at a World Cup had been in the round of 16 of the 2014 tournament in Brazil. The right back was injured before the 2018 World Cup in Russia.
NEYMAR THE STAR
Neymar joined his teammates at the stadium for the first time since injuring his right ankle in Brazil's opener against Switzerland.
He wasn't limping as he got off the team's bus and even played with the ball as his teammates warmed up. The crowd cheered loudly when the stadium's big screen showed him singing the national anthem before the match. He later sat in the stands behind the bench, with fans trying to get close and take photos of him.
REMEMBERING PELE
Brazilian fans showed their support for soccer great Pele, who is hospitalized in Sao Paulo with a respiratory infection.
They displayed a banner with the image of Pele holding a soccer ball behind one of the goals, and opened a large flag with an image of the Brazil great and the words: "Pele. Get well soon." One fan in the stands held up a jersey with a photo of Pele on it.