The 42-year-old "Annie" actress is engaged to boyfriend Benji Madden, sources confirmed to Us Weekly.
"Everyone thinks it's wild but are so happy for them," a source told the mag of the two, who first went public as a couple this past May.
"Benji always tends to fall in love easily, but this time it's for real and he landed a great girl. They obviously both make each other incredibly happy and there's nothing better than that."
The two lovebirds were introduced by Nicole Richie, who is married to Madden's brother Joel.
"I'm going to take responsibility for everything," Richie said in an interview over the summer.
Rumors have been floating around for weeks that the starlet was set to wed, especially after she was photographed with some unidentified bling on her left hand.
Cameron Diaz and Benji Madden arrive at JFK Airport on Friday, with Diaz showing off what looks like an engagement ring.
Diaz recently spoke out about her reported fiancé in the January issue of Cosmopolitan but made sure to steer clear of answering questions about an engagement.
"Timing is everything," she explained. "If you get into a relationship where you want something the guy doesn't want, it's never gonna work."
"No matter how old you are, finding the guy who's in the same place as you are and wants to show up is the only way a relationship works, period," she added.
Prior to dating the Good Charlotte rocker, Diaz was romantically involved with Matt Dillon, Justin Timberlake, Alex Rodriguez and Diddy.
