According to a British newspaper The Sun, the two stars were seen, Wednesday, January 5, celebrating their good news in a Los Angeles restaurant with friends.
This same source stated that Diaz was proudly wearing her diamond engagment ring.
A close friend revealed, "Justin and Cameron are really happy. They spent a lot of time together over the holidays and they decided the time was right to get engaged. Justin spent a fortune on the ring. Cameron was thrilled with it."
Cameron Diaz, 32, and Justin Timberlake, 23, have been dating for almost 2 years.