The actor was recently voted the hottest bachelor by People magazine while Vergara recently broke-up with Nick Loeb.
The 37-year-old actor and Vergara, 41, were apparently introduced at the White House Correspondents Dinner in May, but Vergara was then with Loeb, reported Us magazine.
"It's very, very new. They're having fun and getting to know each other," a source said.
Manganiello recently visited Vergara over the July 4th holiday weekend. They were spotted dining together on Sunday, July 6.
"They were very friendly and took pictures with other diners," an eyewitness said.