Mr. Olivetto was found in a locked bedroom in a house in a Sao Paulo suburb after Brazilian police arrested a half dozen suspects in the kidnapping.
No ransom is
He was reported to be in satisfactory condition, but suffering from exhaustion and high blood pressure.
Early reports said the kidnappers may have been Latin American political extremists rather than a local criminal gang.
Mr. Olivetto, 50, owns one of Brazil's leading ad agencies, W/Brasil, Sao Paulo, and advertising holding company Prax. He is the fourth Brazilian ad agency head to be kidnapped but the first in recent years.
In an escalating wave of crime and violence, more than 300 people were kidnapped last year in Sao Paulo, including the daughter of media baron Silvio Santos, owner of local network SBT.