Ronaldo has been credited with scoring Brazil's first goal in Thursday's 5-2 win over Costa Rica.
Ronaldo's shot deflected off defender Luis Marin and the effort was originally ruled an own goal.
But following a protest by Ronaldo, officials from governing body Fifa watched a tape of the incident and reviewed their decision.
"I have no doubt that I scored the first goal," said Ronaldo.
"The norm is that when a striker kicks a ball, even if it comes off a defender, it is given to the striker because the striker has the intention to score."
Fifa communications director Keith Cooper said: "Ronaldo claimed it in the
dressing room after the match quite vociferously.
"Our technical studies group has come to the conclusion, following the guidelines we have established encouraging positive play, that it was not an own goal and that it was Ronaldo's."
Ronaldo has now scored four goals in the tournament and is just one behind Germany's Miroslav Klose.