Badgley was dating his fellow Gossip Girl star Blake Lively for three years until the couple announced their split in October 2010.
According to Star magazine, Badgley has now moved on to a new romance with McNamee, best known for starring in the popular Australian comedy Packed to the Rafters.
"They were having this deep talk for hours," a source told the magazine, after spotting the couple out on a date in Los Angeles last week. "It was clear they were really into each other."
Earlier this week, Lively was linked to Hollywood star Leonardo DiCaprio after they were spotted hugging at a party on Steven Spielberg's yacht.
Badgley is scheduled to return for the fifth season of Gossip Girl in September.