The reason she's so smitten?
"He's such a man's man, the most macho guy Jenny's dated or been involved with for a long, long time," says the source.
Seems McCarthy, 39, who was linked to several non-famous guys after her five-year romance with funnyman Jim Carrey fizzled in 2010, appreciates that Urlacher is the "strong, silent type" who "quietly takes care of her when they're together," which we assume means he lets her babble away about vaccinations while he nods gravely.
"That may sound old-fashioned, especially since Jenny is very much her own person and a very contemporary, independent woman in many ways," explains the insider. "But she loves the attention and the way he treats her. It's very comforting."
The pair reportedly hit several Windy City hot spots over the weekend, a public stepping-out that came on the heels of McCarthy's admission to Parade Magazine that she's feeling "giddy right now."
"It took awhile," she admitted. "I felt like, 'Oh, I'm so alone I have to be with somebody' ... But I got to a place where I was like ... I'm happy with myself. I don't need to have a lover to have love in my life."
Once Jenny found her happy place, "[romance] kind of worked out," although her 9-year-son, Evan, currently remains in the dark about her love life.
"I have a six-month rule," said McCarthy. "I don't introduce my son to anybody unless someone makes it six months."