According to reports from National Enquirer, his alpine skier girlfriend Lindsey Vonn was spotted making out with an older male backstage at a Justin Timberlake and Jay-Z concert last month.
"She threw herself into his arms and they started on a long session of deep kissing that went on for several minutes. He was a tall, good-looking man, in his mid-40s, with greying temples. They were really going at it," alleges the Enquirer.
However, a rep for Lindsey denies the rumours.
"There is not an ounce of truth in this clearly made up story," says the official statement from Lindsay's camp.
Lindsey and Tiger met at a charity event in 2012, and in recent months Lindsey has spoken about the couple's happiness.
"There's really nothing about him that bothers me," she said in an interview. "He doesn't even leave the seat up! It’s awesome."
Vonn even hinted that Tiger might be cheering her on from the sidelines at the Sochi Winter Olympics in January 2014.
"We're going to see how his schedule goes, but he's hoping to come," she told People magazine.
Tiger's marriage to Elin Nordegren famously crumbled in 2009 after he was found cheating with a string of mistresses.