The interview, printed in the Norwegian magazine Mann and top-selling Swedish tabloid daily Aftonbladet, was "totally fake," said Eirik Lae Solberg, spokesman for Microsoft Norway.
In the four-page interview entitled "Big Bill," author Bjoern Benkow claimed he spoke to Gates during a two-hour commercial flight in Europe.
Gates was quoted as saying in the article that he never carries more than a "dime" in his pocket and that he makes $1 bets with his wife.
He also purportedly talked openly about competition with search engine Google (GOOG) and Europe's antitrust actions against the software company.
The article, which was in Norwegian, quoted Gates as saying, "Google have been smart."
According to Solberg, Gates' personal assistant Craig Beilinson informed Microsoft Norway that the interview never took place and that Gates did not fly in a commercial carrier at the time the journalist allegedly met him.
Earlier, he told Norwegian newspaper Dagens Naeringsliv that the piece was real.
The editor of Mann, Knut Christian Moeng, said the monthly is printing a retraction in its August issue, apologizing for the article.
Solberg said Microsoft Norway would be "pleased" with the apology.
But Olof Brundin, a spokesman for Aftonbladet, said the newspaper was convinced the interview had taken place.
"This is a very respected reporter ... with a very good record," Brundin said. "There is no reason whatsoever for us to doubt him."