The 31-year-old striker tripped and fell during a run in the 44th minute at the Centenario Staidum and was immediately surrounded by players from both teams as he held his left knee.
Neymar was carried off on a stretcher with both of his hands on his face. Richarlison came on to replace him.
Brazil’s medical team had no immediate update on Neymar’s condition.
Neymar, who plays for Al Hilal of the Saudi Pro League, was criticized by fans before the World Cup qualifier because of his subpar performance during Thursday’s 1-1 draw between host Brazil and Venezuela.
Neymar made his national team debut in 2010 and has 79 goals in 128 appearances for Brazil.