The Ibope poll published by the newspaper Estadao showed mixed feelings in Brazil after having hosted the first Summer Games in South America.
The survey also reveals that 57% felt that promoted the international image of Brazil.
On how the Olympics were developed, 42% considered good or excellent, 30% said more or less and 24% poorly.
The survey was conducted between 11 and 15 August when the Olympics, which end Sunday, were halfway.
Marcia Cavallari, director of Ibope Intelligence, said that the "ambiguous" results are explained in part by the games held in Brazil at a time when the country goes through its worst recession in decades.
"They do not clearly see the benefits that the country can expect with events of this magnitude."
"There is overwhelming support (games), but there are doubts about the use of public money for such events when there are other priorities, especially considering the economic crisis," she said.